Are NPC leaders really trying to resolve plaster problems, or will they continue to ignore and/or misrepresent the research studies that have already provided the answers? The NPC says that there has been decades of debate regarding plaster problems. Actually, there have been decades of pool plaster studies, but no honest discussions or debates, and no accountability.

There was a time when NPC leaders understood that improper plaster workmanship can cause plaster defects and discolorations. In fact, the 1998 NPC Technical Manual acknowledged that delaminations, calcium nodules, cracking, flaking, and graying (mottling) of white plaster were due to improper workmanship practices (which is consistent with ACI and PCA literature).

But that changed in 2002 when a new NPC Technical manual was written. The correct information on the causes of the above plaster defects was removed, and now states that aggressive water causes those plaster defects, including white spotting. The NPC made those changes without any new supporting evidence.

Let’s note that the American Concrete Institute (ACI) and Portland Cement Association (PCA) do not blame rain water (which is significantly aggressive) for causing the above defects on cement surfaces. Instead, they cite improper workmanship and/or material additives issues as causes.

In 2003, the IPSSA organization and other groups wrote to the NPC requesting the supporting documentation for the changed positions on those plaster problems, and information that contradicted ACI and PCA guidelines on workmanship practices. The NPC responded that they would not provide any evidence for the new Manual changes, and that there would be no further discussion or debate.

The NPC then decided to conduct test pool studies at Cal Poly to try to prove their theories. But just like the studies conducted during the 1990’s, the results didn’t turn out the way the NPC had hoped. Now the NPC wants to do even more test pools instead of abiding by their own studies’ results, and even though they have already conducted “aggressive water” test pool experiments at Cal Poly.

The reality is that those study results showed that aggressive water did not cause white spotting (spot etching), or cause the other above plaster defects when proper workmanship was performed. Also, some of the balanced water pools did result in white spotting, which indicates poor workmanship was the likely involved. The NPC has been silent about those results.

Also, the NPC also participated in a separate study and learned that the Bicarb Start-up program was superior to the Traditional Start-up for the protection of new plaster, yet they don’t recommend it.

It is obvious that the NPC leaders don’t want the Cal Poly research results scrutinized and revealed, and don’t want to acknowledge the findings by four prominent cement labs (who specialize in forensic analysis) that identified improper workmanship practices as causing white spots, and that aggressive water chemistry was not the cause.

The time for test pool studies is over. The NPC should step up and accept the truth and reality of what has been proven by every study conducted. They need to accept responsibility for plaster defects that are caused by poor workmanship practices. Until then, uninformed pool owners and service techs are continuing to be misled and victimized.

With a lot of publicity and fanfare, the National Plasterers Council (NPC) recently invited the onBalance group to participate in new test pool studies to determine the cause of plaster spotting, which they claim is caused by aggressive pool water.

The NPC wants the test pools plastered with good workmanship and supervised by onBalance, and then they want the pool water to be maintained aggressive (per LSI) to see if spotting develops on the plaster surface.  The NPC says “the testing could take months or even years to bear results.”

Interestingly, this proposal comes on the heels of the NPC spending about a million dollars of industry money at Cal Poly (NPIRC) for test pool studies over a period of years.  Didn’t they learn about proper and improper workmanship practices and aggressive water during those studies?  So what happened at Cal Poly?  Well, that is just part of many things the NPC is NOT telling the industry.

The NPC says that they don’t want to debate this issue. That indicates that they do not want to address the actual Cal Poly test pool results, and the findings by several prominent cement labs on spotting.  It appears that the NPC does not want this information made available to industry professionals and cement/plaster experts to review and evaluate.

There are a number of things that the NPC leadership has not publicly acknowledged, even to their own members.

1. Starting in 1999, and through 2003, two professional cement scientists, who are experienced in forensic analysis to determine the cause of cement (plaster) problems, began to identify specific improper workmanship practices as leading to the plaster spotting problem.  The NPC has never addressed those lab findings.

2. In 2004, the two Cal Poly professors concluded in Phase 1 that aggressive water causes “spot etching.” Yet, in a 2005 report to the International Cement Microscopy Association (ICMA), the same two Cal Poly professors contradicted that Phase 1 conclusion by stating that they did not determine the specific causes, whether chemical or workmanship, of plaster spotting.  They also changed the term and defined the spotting problem as “spot alteration” instead of “spot etching.”  The ICMA report mentions that the spots were soft, had micro-cracking, and also mentions improper workmanship issues as possible causes of the spot alteration phenomenon.

3. The Cal Poly (2004-2005) Phase 2 report concluded that aggressive water has the most profound effect on the “etching deterioration” of pool plaster,” which of course, is true.  However, no conclusion was made in regards to spot etching / spot alteration. The same for Phase 3 and 4.

4. The data within the Phase 2 report indicate that 4 test pools resulted in spotting, yet the water was balanced or had positive LSI water in those pools over an eight month period, which would indicate poor workmanship was involved.  Several other balanced water test pools did not spot, which would indicate good workmanship was performed on those test pools.

5. The data within the Phase 3 & 4 reports indicate that some tests pools had aggressive water about one-half of the time (eight months) and did NOT spot or have any discoloration.  This also would indicate good workmanship was performed in those test pools.  The NPC has not acknowledged this revealing evidence to the industry.

6. In 2012, four prominent cement labs with their scientists (using petrographic analysis) determined similar findings (poor workmanship) on the cause of spotting, and describe the spots as white, soft, porous, and with an abundance of micro-cracks. Why hasn’t the NPC acknowledged and addressed these lab findings?

7. The cement labs did not find evidence of LSI aggressive water as contributing to the spotting problem.  (Of course, LSI balanced water could be defined as being “aggressive” towards the soluble cement compound known as calcium hydroxide, and would dissolve it away from a plaster surface. That process is known as “leaching” which is a term the scientists used in their reports).

8. While the issue and cause of spot alteration is complicated, that is not the only plaster problem that plasterers and NPC inspectors are blaming on water chemistry.  Would you believe that some plasterers are not accepting responsibility for bond failures (delaminations), plaster cracking, gray mottling discoloration, calcium nodules, and spalling (flaking)? According to some NPC consultants and advisors, bad water chemistry causes those problems too.

9. Yes, NPC consultants and inspectors are helping poor quality plasterers get away with bad workmanship. This certainly doesn’t help the quality pool plasterers out there.  It appears that when a plaster job goes bad, the plasterer tries to convince the pool owner that it is a water chemistry problem. Sometimes that doesn’t work, and he calls out an NPC plaster inspector, who convinces the innocent and uniformed pool owner (or service tech in some cases) that all of the available science has proven that aggressive or bad water chemistry causes the above plaster problems (defects).

10. In 2003, the NPC announced that they would not debate anyone about the information contained in their NPC Technical Manual, or about spotting and other plaster defects.  We had information that the NPC Tech manual contradicted literature from the ACI and PCA.

11. A few years ago, the NPC declined a media outlet (Pool Genius Network) invitation for a debate with onBalance in regards to gray mottling discoloration.

12.  In 2011, onBalance extended an invitation to the NPC to participate in a study on a white spotted pool, where plaster samples would be taken and sent to various cement labs for forensic analysis.  The NPC declined.

It appears that the NPC doesn’t want to quickly resolve any of the various plaster defect controversies, which a moderated discussion and sharing of previous test pool studies and science material would do.  The poor quality plasterers and NPC inspectors benefit the most to keep things unresolved because they have the advantage at poolside with uninformed pool owners. 

It is understood that muriatic acid can dissolve and etch a plaster surface.  Therefore, why, after working hard to achieve a smooth, brand-new, hand-crafted, quartz pool-finish, would anyone immediately perform an “acid wash” on that pool?  Yes, that would increase the exposure of the quartz color; but isn’t that shortening the life of the plaster and causing future problems?

Although acid washing of older plaster pools can be helpful to remove stains and scale, and restore the original appearance; that process, unfortunately, will make the surface more porous and prone to future streaking, blotchiness, and staining over time.

If a plaster surface begins to show light color blotchiness or streaking within a few weeks or months after completion, the acid wash or acid bath treatment that was performed when the pool was new may the cause of the discoloration problems.

As is known, new plaster/quartz pools can be more easily damaged by acid than one that is even a month old.  That is why the NPC recommends the Traditional Start-up program in order to prevent acidic and aggressive water from damaging a new finish.

Fortunately, there are better methods that will achieve exposure of the quartz color and retain a smooth and durable surface without damaging the pool finish.

Step 1: During the finishing process, properly time the troweling process to remove the weak, watery cement “cream” (known as laitance) that develops on a cement/plaster surface. The cement cream that accumulates on the trowel while hard troweling should be discarded. 

Leaving a thin layer of cream on the surface while troweling not only prevents the color of the quartz from showing, but creates a weakened surface that will break down, deteriorate, and likely become unsightly over time.

It is commonly believed that as plaster hardens and “cures,” it will naturally release a cement component known as calcium hydroxide, which then results in “plaster dust” forming throughout the pool. That is not necessarily true.

Calcium hydroxide can be prevented from leaving the plaster surface in the first place, and instead, be chemically converted into calcium carbonate (a much harder material) within the plaster matrix. When this is achieved; the surface is harder and smoother, and no plaster dust develops to foul the surface.

Step 2: Preventing calcium hydroxide from leaving a plaster surface can be achieved by the following.  Create a “thick” plaster mix, and do not add calcium chloride.  Do not add water to the plaster surface and trowel it into the surface.  Delay the filling of the pool for at least 6 to 8 hours after finishing. (If the weather is hot and dry; tent the pool!)  Fill the pool with +0.5 LSI water. (The Bicarb Start-up recommended by onBalance will accomplish that).

Step 3: A pool cleaner can be used to continually polish the plaster surface over time to maximize the quartz or pebble color.

If the above recommendations are followed, there will be no need to perform a “No Drain acid bath” (also known as Acid Start-up or Zero Alkalinity Process) after the pool has been filled in order to eliminate plaster dust problems and expose the quartz color.  

The benefit of following the above recommendations is a pool finish that is smooth, dense, durable, and stain resistant. The color of quartz will be vivid, consistent, and long-lasting, and that is what will make a pool owner willing to pay a premium for a special quartz finish.

Note the good color of the light blue quartz pool finish in the picture below.  This pool is ten years old, had no CC added to the plaster mix, no wet troweling, a 12 hour delay water filling – with the Bicarb Start-up process.  An acid wash or acid bath treatment has never been performed on this quartz pool.

There are proper steps to follow for the making of quality pool plaster, including color, quartz, and pebble finishes.  There are also improper practices that can lead to early deterioration and discoloration. Following is a ten-point checklist that will help achieve a smooth, long-lasting, and discoloration-free swimming pool plaster.

1. Plastering in extreme weather conditions can lead to quality and durability problems. The ACI and PCA have specifically warned against using cement-based products in temperatures considered too hot or cold.

One solution is “tenting” the pool, which protects the plaster surface (and the plasterers!) from the elements. In extreme dry heat, tenting the pool, and perhaps directing air from an evaporative cooler beneath the tent, will help the plaster retain its moisture, and properly cure and harden.

2. The best cement/aggregate ratio is about 1 part cement to 1.5 parts aggregate (marble or limestone sand). If the plaster is too rich (cement-heavy), it tends to shrink and crack. If it’s too lean (more sand), it will be less durable and potentially unworkable.

3. When mixing plaster, a thick mix is best. Achieve a water/cement ratio of .48 or less. Both the American Concrete Institute (ACI) and the Portland Cement Association (PCA) maintain that lower water/cement ratios produce better-quality cement that can withstand occasional exposure to aggressive water.

Lower water/cement ratios boost density while reducing permeability, porosity, shrinkage (craze cracking) and water movement within the cement product. Higher water/cement ratios, by contrast, cause excess shrinkage and cracking, and fail to offer adequate protection or long-term durability against the effects of water and the environment. 

4. A plaster mix should be mixed thoroughly, but also not too long. It is recommended that if the plaster has been mixed for more than 90 minutes, the plaster mix should be discarded. 

5. Plaster should contain as little calcium chloride set-accelerant additive as possible – and never more than 2 percent to the amount of white cement. According to the PCA and other testing facilities, too much calcium chloride increases gray mottling discoloration and cement shrinkage. Colored plaster, of course, should not contain any calcium chloride due to severe mottling effects. Several alternatives to calcium chloride that do not exhibit these characteristics are now available.

6. Never add water to plaster surfaces while troweling. Both the ACI and PCA have found that this can increase porosity, shrinkage, and variable discoloration.

Never “work,” or force, additional water into the plaster surface when troweling. Doing so can weaken the surface and may accelerate deterioration and caused spotting or streaking discoloration. Dark color plaster is even more susceptible than white plaster to white spotting and blotchy discolorations due to water troweling.

7. Well-timed hard troweling can produce a smooth and dense plaster finish. But if the plaster becomes too hard before the surface is smooth, the result is often dark gray discoloration and spotting, especially when calcium chloride is also used.  Cement “cream” (laitance) that accumulates on the trowel should be discarded and not re-applied to the surface. 

8. Don’t fill the pool with water too soon. A new pool plaster surface is soft and vulnerable to being dissolved by water. Though conditions vary, filling should not be started for at least six to eight hours after the pool has been plastered and finished, even in hot weather. This should be enough time for the plaster to harden properly before being submerged in water.

Shrinkage cracks are more likely caused by high water mixtures and water troweling than being allowed to harden before submerging in water. Consider cement flatwork applications in comparison.

Even balanced fill water can dissolve soluble cement components (calcium hydroxide) if the surface has not adequately hardened. The end result is often greater porosity, early deterioration, and discoloration. And it only takes a few months to become visible.

9. Soft or aggressive fill water can harm new plaster surfaces. By contrast, baking soda startups will adjust the fill water to promote a superior plaster surface.  Other new plaster problems such as drips, splotches, spotting, trowel marks, and hand- and footprints are the result of localized troweling and finishing errors.

Acid treatments of newly finished quartz finishes etches a plaster surface and can cause color differences and streaking that may not be visible until weeks later after the pool is filled with water. Those techniques simply age and shorten the life-span of pool plaster.

10. Once the pool is filled, balance the water (and keep it balanced). Balanced water helps help preserve the plaster. Aggressive water causes uniform etching, while over-saturated water scales the plaster. The Saturation Index is a good guide – to prevent scaling or etching, water should have a saturation index value in the range of -0.3 to +0.5.

With reasonably consistent maintenance, pool plaster has a life span of approximately 20 years. It’s an inherently strong surface, and should be able to withstand “real world” chemistry and/or maintenance challenges.

Although pozzolans and other materials such as quartz and pebble aggregates are generating good results, solid workmanship is still required. The above guidelines will benefit pool plasterers in the pursuit of a discoloration-free and durable pool finish.

Good things are happening in the pool industry.  At the Western Pool & Spa Show in Long Beach last month, several knowledgeable pool plasterers publicly stated that improper plastering practices will lead to various discolorations and poor quality pool plaster.

Ed Rock, owner of San Rock Plastering in Los Angeles County, taught a class on proper and improper pool plastering practices. He stated that if his troweling crew “burns” (overly late hard troweling) the plaster and causes graying, it is not just time for a re-plaster, but also time to retrain his crew.  He also stated that “organic” color pigments, while inexpensive, are extremely problematic (severe mottling, spotting, or blotchiness) and should not be used in swimming pool applications. 

It was pointed out that adding calcium chloride (hardening accelerator) to color pigmented plaster (including in quartz and pebble applications), and adding water to a plaster surface while troweling is detrimental and will lead to white blotchiness or spotting.

In our (onBalance) class on plastering, a plasterer commented that he does not add any calcium chloride to his plaster mixes because of the problems that can be caused. Many plasterers are now using a “non-calcium chloride” accelerator with great results, especially with color pigmented plaster. It was also acknowledged that calcium nodules are due to delaminations and cracking issues.  

Several plasterers (and many service techs) stopped by our booth to mention that they have had great success using the “Bicarb Start-up” program on their newly plastered pools (including Quartz and Pebble). They are amazed on how there is no plaster “dust,” and that dark colored plaster jobs remained dark and uniform. They changed to the Bicarb Start-Up because of problems with the “Acid Wash” and "Acid Bath" program which often results in light colored blotchiness or streaking that develops later.

It was very refreshing to hear plasterers acknowledge that certain plaster discolorations and defects are due to poor plastering workmanship or materials, and not due to unbalanced water chemistry maintenance, start-ups, or high cyanuric acid levels.

An article in the March 2014 issue of Concrete International (ACI) also points out the importance of proper troweling techniques and timing, and not adding water to the finish while troweling in order to avoid color variations (mottling) in cement flatwork applications. 

Plasterers with integrity (like Ed Rock) accept responsibility for plaster defects, and won’t blame innocent service techs and pool owners who maintain the water chemistry. And because of that, they are more motivated to teach and ensure that their finishers follow proper plastering procedures.

Consequently, quality plasterers have few problems (if any) that begin to appear a few weeks after completion, such as gray mottling or white spotting (spot etching). When nothing goes wrong, there is no need to blame someone. The above bodes well for our industry if more leaders from the plastering industry speak out and teach others in an effort to improve plastering standards.

Contrary to some misinformation that has lately been floating around, high cyanuric acid (stabilizer) levels do not cause gray discoloration, or white spotting (“spot etching” as some incorrectly call it) in plaster swimming pools, no matter what.  And there are several studies that have documented that.

The NPC/NPIRC Cal Poly Phase 4 study (2006-2007) showed that 250 ppm of cyanuric acid (CyA) didn’t cause gray discolorations or white spotting. In fact, in comparison to pools with zero, 50 ppm, and 100 ppm of CyA, the plaster pools with 250 ppm CyA looked the best overall after ten months.

A study by onBalance included placing a quality plaster coupon into (balanced LSI) water with 150 ppm of CyA, and an identical coupon into aggressive water (low TA) with 300 ppm of CyA. They were left there for one year. The picture below shows that the coupon submerged in 150 ppm CyA remained uniformly white and smooth (non-etched), and although it is hard to see, the coupon submerged in 300 ppm CyA had slight uniform etching and some exposed aggregate showing at surface. Note that neither of the plaster coupons resulted in gray mottling or white spotting.

The Dow Whitney study (University of Florida, 1990) concluded that Cyanuric acid alone was not a cause of leaching even at 500 ppm.

Even the 2004-2005 Arch Study provided further evidence that high CyA levels don’t cause gray discoloring or white spotting of pool plaster. Their study did show uniform etching (degradation) of the plaster coupons due to the water being aggressive, but not from high CyA only. It appears that the alkalinity had remained on the low side and was not adjusted upward to balance the water (per the LSI) when higher CyA levels (250 ppm) were maintained.

Why write about this high CyA issue?  Because there is one pool plasterer (and NPC member) that teaches at pool trade shows and at service tech’s chapter meetings that high CyA levels (above 50 ppm) causes gray discoloration and white spotting (spot etching). What studies does he cite as supporting his opinion? The same NPC/NPIRC and Arch studies mentioned above, which in reality, don’t support his claim at all, and in fact prove just the opposite.  

Both white pool plaster coupons below have been in water for one year. Sometimes the water was slightly aggressive (negative LSI), and sometimes the water was slightly scale forming (positive LSI).

The top coupon was formed with only one percent calcium chloride (CC) added to the mix, and was properly troweled.  It remained a “uniform white” the entire time. 

The bottom coupon had 3% calcium chloride (CC) added, was late hard troweled, and also received some wet (water) troweling late in the process.

Note the light and darker color contrast of the bottom coupon creating a “blotchy” appearance. The darker areas are very dense due to the hard troweling. The lighter (white) areas and spots are due to higher water-to-cement ratio and porosity from wet troweling. Had that coupon not been troweled with water, it probably would have been more overall gray due to the high CC and late hard troweling only.

Sometimes, plasterers add 3% CC to a plaster mix to hurry up the hardening process and finish the pool faster. The plaster mix may harden so fast that the finishers can’t keep up. If the plaster is not smooth enough, the finishers may then splash water onto the surface to rework and soften up the plaster again in order to get it smooth.

This experiment demonstrates that improper troweling and workmanship can create non-uniform discolorations of pool plaster.

One would think that when mixing white cement with white limestone aggregate, the final pool plaster product would always be white. But that is not always the case.

Unfortunately, white pool plaster sometimes turns gray (or grey) either immediately or a few months after the pool is filled with water. So what causes that to happen?

The concrete/cement industry has documented that late hard troweling can cause a cement surface to darken, mottle, and spot. Also, adding a high dosage of calcium chloride (CC) to a plaster mix causes a slight darkened (graying) hue to develop. The combination of the two issues is really problematic. The pictures below of plaster coupons demonstrate how white pool plaster can darken and mottle. 

Picture above: Top left coupon: no CC added, properly troweled. Top right coupon: no CC added, late hard troweled. Bottom left coupon: 2% CC added, properly troweled. Bottom right coupon: 2% CC added, late hard troweled. All were placed in balanced water for one year.

Note the darker color of bottom left coupon that had 2% CC added in comparison to top left coupon which had no CC added.  Note the darker color of bottom right coupon that had 2% CC added and received only minimal late hard troweling in comparison to the top right coupon, which had no CC added, and received four times the amount of late hard troweling.

Picture above: Note that the top coupon is the whitest. That coupon had zero CC added and was properly troweled. The middle coupon had 2% CC added, received some late hard troweling. The bottom coupon had 2% CC added, received some late hard troweling, and placed in balanced water for one year. Note how the bottom coupon darkened even more after being submerged in water.

Pool owners pay good money for uniform white plaster, not gray, blotchy, or discolored plaster.

One of the most absurd conclusions by the NPC/NPIRC study has to do with the causes of craze cracking (shrinkage cracks) in pool plaster.

It has been known for decades in the cement/concrete industry that high water to cement ratios, calcium chloride additions, excessive wet troweling, and hot and windy weather leads to increased shrinkage cracks and other problems (ACI 302.1R-04).

Yet, the NPC and two Cal Poly professors disregarded that established science and tried to connect certain sanitizers as causing increased craze cracking! The Phase 2 study report states that Salt systems resulted in the greatest amount of craze cracking (and also etching and discoloration); with Bleach, Trichlor, and Cal Hypo somewhere in the middle, and Dichlor with having the least amount of craze cracking (pg. 43 & 85).

How in the world could the chemistry professor think that different sanitizers affect plaster differently? He would know that all chlorine sanitizers add the same thing (chlorine) to the water. And since the pH was maintained within the same range in all of the 12 test pools, how could there be any different affect?

And how could the concrete engineer professor go along with that conclusion knowing that shrinkage cracks involve materials, workmanship, and weather? Where in the ACI literature does it say that aggressive rain water causes shrinkage and craze cracking?  It doesn’t. In fact submerging plaster in water helps to reduce cracking.

The Phase 3 study report states that the Dichlor sanitized pools had the most crazing cracks (pg. 57). That is opposite of what occurred in Phase 2!  Wouldn’t that inconsistency raise a red flag? What is their excuse for suggesting that sanitizers increase crazing, and not mentioning a word about workmanship issues as likely causes? And the NPC claims that their study is credible.

Check out the link to what an NPC Technical Advisor wrote on a pool with cracking and calcium nodules. 

http://www.poolgeniusnetwork.com/profiles/blogs/salt-pool-blamed-for-plaster-cracking-and-nodules

The dark colored plaster pool above is an older pool with delamination cracks and calcium nodules growing on them.

It is not the newer "Salt" pool mentioned in the link above.

The NPC has stated that pool water must be maintained with a Langelier Saturation Index (LSI) between 0.0 and +0.3 for plaster pools (no negative LSI is allowed), and that disregarding those LSI parameters promotes white spotting, etching, and discoloration on the negative side. 

Yet the NPIRC Phase 3 (2005-2006) study demonstrated that typical white pool plaster (Section C in Pool 5) can withstand negative LSI’s (from -0.1 to -0.4) one-third of the time over an eight month period without any visible etching, spotting, craze cracking, or discoloration. That pool section was rated “zero” in all three categories.

It is apparent that the workmanship of the white plaster section (C) in Pools 5, 6, and 9 was better than the Phase 2 test pools. According to the report, section (C) was plastered with only one percent calcium chloride added, with a better water-to-cement ratio (.46) instead of (.50). Perhaps better plaster finishers were also used.

By comparison, several test pools in Phase 2 deteriorated and discolored in slightly positive LSI water within just six weeks’ time, and had white spots within four months! 

What the above means is that a negative LSI of -0.1 to -0.3 is not overly aggressive and does not cause white spotting and gray discoloration, as the NPC claims. Those slightly negative numbers are within the “balanced” range (-0.3 to +0.5) as established by the APSP. Furthermore, even very aggressive water does not cause white spotting or gray discoloration. It simply etches a quality plaster surface uniformly over time.

The NPC has ignored the real evidence and misrepresented the results of their own study.  It is time they acknowledge that poor workmanship practices cause specific plaster problems.

NPC Certified Start-up Technicians should be concerned. There are reports that start-up people have been blamed for various plaster problems even though the pool water was properly started and balanced. See “IPSSA Member Victimized for $6,000” Link:

http://www.poolgeniusnetwork.com/profiles/blogs/ipssa-member-victimized-for-6-000

When the NPIRC’s Phase 2 report is completely reviewed, it becomes obvious that the conclusions rendered are not supported by the results of their test pool experiments. It appears that the two Cal Poly professors and NPC leaders confused plaster surface weaknesses, discoloration, and degradation (caused by poor workmanship) with uniform etching (caused by aggressive water).

For example, the reports states that Pools 1, 5, 8, and 12 showed signs of “etching deterioration” in just six weeks’ time after plastering and filling with water. But those pools did not have aggressive water (negative LSI) during the first six weeks! And Pools 1, 3, 4, 5, and 12 had discoloration, all without the water being aggressive. White soft spots (called “spot etching” by the plasterers) were reported in Balanced Pools 1, 4, 5, and 12 at the fourth month inspection.

A review of the results of Spa 13 and Spa 14 is also revealing. Spa 13 was deemed to be the “Aggressive” spa, and Spa 14 was the “Balanced” spa. But the first four months water test results shows that the water in both spas were virtually identical with balanced and positive LSI numbers.

At the six week and fourth month inspections, the NPIRC claimed that Spa 13 had significant signs of etching and discoloration, but Spa 14 did not. Shouldn’t the condition of both spas have been the same since the water balance was the same? Yet, the NPIRC concluded that aggressive water caused the unsightly issues in Spa 13 even though the water was balanced.

It is very curious that the professors and NPC leaders did not consider improper workmanship practices as causes of the discoloration and degradation of their test pools since the water was balanced with positive LSI’s, and especially since the cement/concrete industry has documented issues like this. Didn’t they review the water chemistry data? Were they just unaware of the facts, or was it something else?

The twelve pools and two spas had different plaster finishers working in them. They claimed to have videotaped the plastering. Shouldn’t they have reviewed that and learned what went wrong, instead of blaming the water chemistry?

After their first year of study, the two Cal Poly professors wrote the NPIRC Phase 1 report, for the NPC, suggesting that aggressive water was the primary cause of “spot etching” in their plaster test pools… which of course, is what the NPC wanted.

Six months later, however, the same professors (along with a petrographer) wrote a separate report (regarding the same Phase 1 study), and presented it to the International Cement Microscopy Association (ICMA), but did not make that same claim.

Instead, they stated that the specific cause(s) of “spotting” could not be determined due to poor water maintenance and record keeping!  They also did not refer to the spotting problem as spot “etching,” but instead, referred to it as spot “alteration” and described the spots as being “soft.”

Additionally, the professors acknowledged (as does the cement/concrete industry) that improper and excessive finishing techniques, high calcium chloride content, and uneven moisture content can lead to excessive shrinkage, cracking, discoloration, permeability, and to a wide range of progressive deterioration mechanisms. That is quite a change in opinion from the NPC report to the ICMA report.  Why?

Since NPC leaders are unable to refute the evidence that the study is flawed, and needing a way to avoid further discussion, they often claim that everything was unanimously approved by the NPIRC committee.  But even that claim is not true.

There were members of the committee that disagreed with the first protocol and conclusions.  Lee Wikstrom, Ph.D., saw problems with the study and voiced them at their meetings.  The NPC stopped notifying him of future meetings and was dropped from the committee. (They have also removed industry people from other committees before). Apparently, that is one way to control the outcome of research conclusions and suggest unanimity.

In our next post, we will illustrate how the NPC and Cal Poly professors must not have understood the difference between an etched plaster surface (caused by aggressive water), and a deteriorated surface caused by improper material and plastering practices. 

onBalance

Years ago, pool service techs learned that aggressive water etches quality plaster surfaces uniformly - that it does not pick and choose some areas of the surface to etch, while leaving other areas untouched.

The cement/concrete industry documented that improper workmanship practices can cause cement surfaces to mottle, darken, discolor, deteriorate, streak, and spot.

Yet, in the 1980’s, when pool plastering companies began seeing white spots in some of their recently plastered pools (white and dark colored), they decided that aggressive water was responsible; rather than poor workmanship. The plasterers even invented the term “spot etching,” without any evidence that white spotting was an etching phenomenon at all.

Even after two professional cement analysis labs determined (by 2003) that improper plastering practices actually caused the weaknesses that result in porous white spots developing over time, the National Plasterers Council (NPC) refused to accept that science and decided to sponsor a study on spot etching at Cal Poly in San Luis Obispo (NPIRC).

Later, the NPC announced that the NPIRC study proved that aggressive water was the primary cause of spot etching.  But their claim is incorrect. The NPIRC’s test pool experiments proved just the opposite. Some test pools maintained with balanced water developed some white spotting and gray discoloration, and some test pools with aggressive water did not develop any white spotting or gray mottling.

If you have read onBalance’s recent (2013) articles titled “White Spotting of Pool Plaster” and “Scientific Evidence of Spotting,” you would know that four prominent cement labs and petrographers (with PhD’s) have now independently and scientifically determined that improper plastering practices cause white, soft, and porous spotting. The NPC cannot refute those findings.

Many pool industry companies (including reputable plastering companies) donated hundreds of thousands of dollars to the NPC, thinking the NPIRC study would be scientific, non-biased, and credible in finding causes and solutions to plaster problems. Unfortunately, many have been fooled by NPC’s claims. What a waste of money; and the NPC/NPIRC study didn’t even contain information on proper or improper workmanship practices.

The swimming pool industry has been duped; service techs and pool owners are being deceived, incorrectly blamed, and scammed; sometimes costing them thousands of dollars for a re-plaster, because plasterers with poor workmanship are not being held responsible.

In future posts, specific details on the actual results of NPC’s study will be provided, including how their conclusions are flawed.

Comments and questions are welcomed.

In order to ensure a long-lasting and stain resistance finish, new quality pool plaster (including quartz and pebble) requires at least six to eight hours of proper curing (humidity) before filling with water, and requires the fill water to have a positive Saturation Index (LSI) of about +0.5.

If new pool plaster is submerged in water too early, or the fill water is low in calcium hardness and alkalinity (negative LSI), some plaster material will dissolve from the surface, creating porosity and weakness, and will then be more susceptible to future staining or lightening.  All of this occurs before the service tech arrives to perform the chemical start-up program.

Can a service tech know if some plaster material has been dissolved off the plaster surface?  Yes, by the amount of “plaster dust” that has settled on the bottom of the pool.  More damage can occur to a new plaster surface during filling than during the following month.

The reason that a new pool plaster surface is so vulnerable at first is due to the fact that it contains about 15 to 20 percent calcium hydroxide.  Calcium hydroxide is soft, slightly soluble, the weakest component of pool plaster, and is dissolved by typical fill water at the surface.  The LSI is applicable to calcium carbonate, not calcium hydroxide.

As much as 20 pounds of calcium hydroxide can be dissolved from the plaster surface of a 20,000 gallon pool, depending on the workmanship, fill-delay, and aggressive fill water conditions. The calcium hardness of the fill water can increase 50 ppm to 100 ppm upon filling. 

It is the dissolved calcium hydroxide that becomes “plaster dust” (in the water) as much of it is transformed into insoluble calcium carbonate by the pool water.  The amount of plaster dust formed can indicate how much material has been lost from the pool plaster surface. The more material that is lost, the more porous and rougher the plaster surface is (as seen under magnification), the less durable it is, and the more likely dirt, iron, and copper will stick to the surface as time passes. And weeks or months later, when the plaster surface begins to look aged and stained; the improper filling program the pool received may be overlooked as the cause. 

A Bicarb Start-Up chemical program (as promoted by onBalance) ensures that the fill water is appropriate (a positive LSI) for filling a new plaster (and quartz) pool.  It prevents the loss of calcium hydroxide from the plaster surface, which preserves a dense (non-porous) surface, and with no plaster dust forming.  It does that by converting calcium hydroxide on the plaster surface into calcium carbonate, creating a harder, denser, smoother, and more durable surface.  If everything is done correctly, there will be no increase of calcium hardness in the pool water.

Because the plaster surface is smoother, dense, and more durable, it stands up better to future acid washes and dirt and mineral stains are easier to remove. Dark colored plaster stays darker and does not become blotchy or lighter in color.  Long-term esthetics is definitely improved.  Acid start-ups can be one reason for colored plaster and quartz finishes becoming blotchy and lighter in color.

For the past 15 years, many pool plasterers and service techs report having great success with the Bicarb start-up method. 

For the Bicarb start-up: http://www.poolhelp.com/handouts/oB_Bicarb%20Startup%20Method%20Handout.pdf

The above pictured pool/spa combo, featuring black plaster, was set up as a Bicarb start-up. You can see the barrel and hoses in the background. When we came back, the pool was crystal clear, but the spa looked like it was full of milk (especially once we brushed it!). The homeowner had come home and decided to fill the spa using non-bicarbonate tap water. What a difference!

The first picture shows white streaking on dark colored plaster caused by excessive and inappropriate water troweling, and the addition of calcium chloride to color pigmented plaster. In time, the color pigment is dissolved and lost from the plaster finish due to the porosity caused by the above issues. This shows that “white streaking” can sometimes occur as opposed to “white spotting.”

The second picture shows white soft and porous areas on the floor of a white plaster pool.  The pool plasterer had sprayed down the new finish with water before filling (because some leaves blew in), which should never be done.

The third picture is of the top step of the same pool.  Note the upper right corner has small white soft spots.  That area of the step is slightly lower than the surrounding step area, and the water collected  (puddled) there after being sprayed down. I believe this area was also negatively affected by being submerged in water too soon after finishing.

The white porous areas in this pool did not begin to appear until about two months after completion.  This particular pool was filled with hard well water, and never had aggressive water. How do I know that? It was my personal pool built twenty years ago. 

A cement lab determined that the pool plaster contained an excessive amount of calcium chloride (3.5%), the surface had not been etched by aggressive water, the white areas were soft and porous, and had simply degraded over time. 

Because these types of discoloration problems don’t become visible immediately after plastering, some industry members believe that “imbalanced” water chemistry has to be the cause.  It needs to be understood that aggressive water doesn’t cause white discoloration. 

Instead, improper water-spraying new pool plaster, filling too soon, adding too much calcium chloride, and water troweling, can eventually lead to “white discoloration” (porosity) issues on new white or dark colored pool plaster, including quartz. 

A CPO and IPSSA member had contracted with a pool plasterer to re-plaster a swimming pool near Los Angeles.  Within a week after plastering, the IPSSA member notified the plasterer that he could see some long cracks in several locations.  The plasterer told the IPSSA member that the cracks would close and disappear in time. Two years later, the IPSSA member took these pictures of the quartz aggregate pool.

Note that the plaster coat has cracked and is delaminating away from the pool wall.  When the plasterer was questioned about the obvious cracking and bonding problem with the new plaster, he suggested calling an independent plaster consultant who was also an NPC Board member to inspect the damaged pool plaster.

During his inspection, the consultant acknowledged the presence of a significant two foot-long plaster crack running down the wall and missing tile, but instead, focused on the signs of “etching and associated discoloration” of the plaster surface.  The pool did have some smooth gray mottling discoloration in parts of the pool, but there were no signs of etching.  The pictures seem to bear that out.

The consultant blamed the gray discoloration and (supposed) etching on the fact that the pool was filled with low calcium (80 ppm) tap water and that the water was not properly balanced at start-up. Yet, the IPSSA member had records showing that he added 20 lbs. of calcium increaser at start-up to raise the calcium hardness level to 200 ppm. The consultant refused to accept the IPSSA member’s account.

The consultant claimed that the (CYA adjusted) “carbonate” alkalinity was only 67 ppm, and the calcium hardness was 150 ppm, which he claimed were below national standards, making the water aggressive.

As a remedy, the plaster consultant recommended that the pool undergo a “Zero Alkalinity” process to clean up the etching and associated discoloration.  Huh?  Make the water extremely aggressive to clean up etching and discoloration which was caused by aggressive water? He also suggested “sealing” the cracks to stop the water leakage.

The consultant’s report states that he “saw no evidence of improper workmanship or materials with the plaster application.” The plasterer then refused to be held responsible for any issues with the pool.

About two months later, chunks of plaster began to fall off the pool wall.  Because the IPSSA member was the remodeling contractor, performed the chemical start-up (Traditional), and had sub-contracted out the plastering, the pool owner demanded that the IPSSA member resolve the problem.

The IPSSA member paid out about $6,000 for another plasterer to re-plaster the pool. Samples of the old plaster were sent to a cement lab that determined the plaster surface was not etched. The plaster did contain 2.5 percent calcium chloride, which is known, along with late and overly hard troweling, to cause smooth gray mottling discoloration, which this pool apparently had.  Of course, the major cracking and delamination was the more critical problem, but the consultant apparently felt otherwise.

The IPSSA member initiated a lawsuit against the plasterer, but became intimidated when an attorney, popular among plasterers in the area, threatened a counter lawsuit (frivolous and harassment).

It is alarming that without any supporting evidence or documentation, the NPC’s Technical Manual and other NPC literature suggests that slightly negative LSI water (-0.1 to -0.3) can cause spalling, flaking, cracking, white spotting or streaking, dark gray discolorations, and calcium nodules. (How does it decide which to do?) No, the NPIRC at Cal Poly has never proven anything remotely close to that.

Poor pool plaster workmanship practices continue to be enabled and protected by the NPC and their consultants.

When a new white quartz pool in San Diego developed numerous shrinkage cracks and very rough and sharp calcium nodules everywhere, the plasterer drained the pool and sanded it, charging the pool owner one thousand dollars for the work. The crystalline nodules began to form again soon afterwards, so the plasterer told the pool owner that a pool plastering expert and consultant would perform an inspection to determine the cause.  The plaster inspector was also a long-time National Plasterers Council (NPC) Board member, but it is not known if the pool owner was given that information. 

The inspector reported the following observations and recommendations. 

1. The many random cracks were about 1.5 inches in length and had nodules on them.

2. The pH at the time of the inspection was 7.8, TA 80, CH 600, TDS 4400, (Salt content 2800), and CYA 50 ppm, so he calculated LSI as “0.0” and in balance.  (Actually, the LSI would be about +0.3).

3. He claimed that a high TDS and low “carbonate” alkalinity (62 ppm) causes calcium to be “leached” from the plaster surface (even though the LSI was balanced). 

4. He told the pool owner to purchase a Taylor K-2005 test kit so that he (pool owner) could accurately test the pool water.

5. He recommended draining the pool, sanding the plaster surface again, filling with fresh water, not adding salt, turning off the Salt System, and then properly maintaining the pool water.  He wrote that, by reducing the salt content, TDS, and calcium, the pool surface should stay smooth.

6. The inspector stated that he “saw no improper workmanship or materials on part of the plasterer.”

After the plaster inspector report was provided, the plasterer stalled and/or refused to replaster the defective pool.  About a year later, the plasterer went out of business.  The pool owner was left with a very unsightly and rough quartz pool. 

Later, a cement lab determined that the plaster mix contained 5 percent calcium chloride, which is excessive, and that the cracking occurred immediately after finishing and before the pool was filled with water.  Excessive calcium chloride additions also contribute to calcium bleeding and the formation of nodules.

What enabled the pool inspector to render that erroneous conclusion?  Disturbingly, the NPC Technical manual contains text that can be interpreted to support the inspector’s position, and enable plasterers to avoid responsibility for defective workmanship, including plaster cracking and nodules.

Are we as an industry going to allow the NPC to blame “plaster cracking and nodules” on water chemistry?

The following information provides pictures and scientific evidence from the cement petrographers who performed “failure analysis” examinations on white spotted pool plaster cores.

The first picture (above) is of a plaster core from the pool that had suffered from white soft spotting.  Note the six major white spots, and also note the general and overall “graying” (off-white) of the plaster surrounding the white spots.  When submerged in water, the gray (or grey) color becomes slightly darker.  The addition of calcium chloride to a plaster mix contributes to graying of white cement.

The second picture is of a cross-section of one of the spots on the core magnified.   The Scale on top of that picture is marked in “millimeter” increments.

The polished side section of the plaster coupon was treated with a solution (phenolphthalein) that imparts a purple-red stain to a high pH, non-carbonated cement paste, and also leaves a faint pink to no color stain on reduced pH, carbonated paste. 

Note the non-colored (white) spot at the top surface of the plaster coupon.  That spot corresponds to one of the white spots in the first picture above. 

The dark purple-black colored layer at bottom of second picture is of the gunite (substrate) of this in-ground swimming pool which was removed during the coring (drilling) process.

The third picture is a close-up of the white spot.  Question: Does the plaster surface on these cross-sectioned pictures appear to be etched by aggressive water?  No, the surface is very smooth considering the magnification of these photos.  Under closer and more detailed examination, the entire white area was determined to be porous, soft, and carbonated (by balanced pool water).  Even some micro-cracks are visible.

The fourth picture below involves Scanning Electron Microscopy (SEM) and includes two Backscattered Electron (BSE) images.  The image on top left in taken at 100X magnification, and the top right image is taken at 250X magnification.  The darker gray plaster paste on top portion of each image is porous and soft.  The lighter colored gray plaster paste towards bottom area is denser, harder, and has not been carbonated.  Note the whitish and dense carbonated layer at center.

The bottom portion of the above image is an Energy-dispersive X-ray spectroscopy (EDS) determining the major cement elements in a specific area. 

All four cement labs analyzed a different plaster core and determined that all contained more than three (3) percent calcium chloride.  (Two percent is the maximum allowable).

The white spots were caused by improper plastering practices, not by aggressive water chemistry. 

See blog "White Spotting of New Pool Plaster" posted on March 23, 2013.

onBalance

The problem of plaster spotting has been an ongoing controversy in the swimming pool industry for over three decades. The generally round, smooth-yet-unsightly white soft spots in new plaster pools have long been a source of contention among pool plasterers, and pool service firms or pool owners, each blaming the other for the phenomenon.

From 1999 to 2003, onBalance provided to the NPC several different pool case studies (performed by two professional cement labs) on white spotting. The studies determined that white spotting was caused by several contributory elements, all due to improper plastering practices: too much calcium chloride added as a set accelerant; adding water to the hardening plaster surface; trowel-pressing the water into the surface, creating porosity and micro-cracking in localized areas or spots which allows for later water penetration into the plaster matrix; subsequent “rinsing” (non-aggressive leaching) of soluble plaster components (calcium hydroxide and calcium chloride) from the thus-compromised surface; and late hard troweling.

Over the course of the past year, onBalance undertook an additional project to provide additional evidence.

A one year old spotted pool in Los Angeles was inspected by both an onBalance partner and by a pool plastering industry advocate. Both had produced written opinions on the pool in question, with the former implicating defective plastering workmanship and the latter implicating aggressive water chemistry.

At that point, onBalance drained the pool, and with representatives of the trade press, service members, and pool plasterers present, core sampled the pool, obtaining dozens of cores from a spotted pool wall. These samples were sent to four different cement failure-analysis laboratories for petrographic examination. Results have been obtained from Construction Technologies Laboratories (a subsidiary of the Portland Cement Association), the RJ Lee Group, Riverbend Petrographics, and Wiss, Janney, Elstner. Would these highly respected labs find consensus when independently analyzing plaster cores containing white spots?

All four labs have now submitted reports on their analysis. Here is a summary of their findings:

1. The pool plaster contained more than 3 percent calcium chloride dehydrate, which is detrimental. (The allowable maximum is two percent, and zero for colored plaster).

2. The whitish spots were smooth to the touch, but under a microscope, the spots were shown to be porous, permeable, structurally weak and soft, with an abundance of micro-cracking and a high water-to-cement ratio.

3. The depth of the micro-cracking and porosity within the spots went as deep as 5 mm (.2 in. or 3/16^th) and a diameter (width) of 15 mm (.6 in.)

4. The unaffected surface (cement paste) surrounding the spots was dense, hard, and smooth, and did not have a high water-to-cement ratio, the porosity, or the micro-cracking as found in the spots.

5. There was no evidence of aggressive water or chemical attack (relative to calcium carbonate) causing the spots. The surface areas surrounding the spots was not etched, but instead had been “carbonated” which provided further evidence that the surface had not been etched by aggressive water.

6. The improper adding of water during plaster finishing (troweling) causes excess porosity and micro-cracking within the spots. This in turn, provides an avenue (breach) for pool water to penetrate deeper into the plaster matrix and access soluble compounds causing continued loss of plaster material.

As indicated above, improper water chemistry did not cause the white spotting. In fact, balanced pool water – and even water with a positive LSI value – will not stop this process from happening to a defective plaster surface. And depending on the severity of the plastering mistakes, spotting may develop and become visible within a week of filling with water, but usually a few months later.

White spots have a smooth, yet porous surface. This is due to the loss of two soluble plaster components (calcium chloride and calcium hydroxide, which comprise of about 15 – 20 percent of the cement) interspersed throughout the more durable materials. This results in a weakened, soft, and self-deteriorating surface.  Porosity, and subsequent carbonation, creates a lighter (whiter) color in contrast to the surrounding denser and unaffected plaster surface.

While white spotting is somewhat visible in white plaster pools, it becomes more unsightly when the surrounding surface is off-white and slightly gray due to excess calcium chloride being added to the plaster mix.  And since the spots are more porous than the surrounding plaster, it can also absorb copper or iron and become aqua or brown instead of white. Spotting is especially visible and objectionable when it occurs in dark colored plaster and colored quartz pools.

By comparison, aggressive water attacks and removes most plaster compounds from a dense and smooth surface, thereby causing a uniformly etched and roughened surface, similar to fine sandpaper, and with no significant change in color. As is known, when dark colored plaster pools are given various types of acid treatments, they do not turn white, nor do they spot.

The plastering industry has no study that proves aggressive water causes random white spotting on quality pool plaster. There seems to be little doubt that the cause of plaster spotting has been discovered, analyzed, identified and verified.

The concept of the “Zero Alkalinity” process (also known as a No Drain Acid Wash or Bath) is to make pool water aggressive enough (by adding acid) to dissolve and remove stains or scale from older cement-based plaster surfaces, including quartz and pebble swimming pools.  Unfortunately, this process generally removes some of the plaster surface material.

Assuming a total alkalinity of 100 ppm, it requires 4 gallons of muriatic acid (31.45% strength) per 20,000 gallons of pool water to reduce to zero alkalinity, and to a pH of 4.5.  That acid treatment over a 7 day period can dissolve and remove about 8 pounds of plaster material (equivalent to 50 ppm of calcium carbonate) from a fully cured surface.  So is that good or bad for a plaster pool? 

The reality is that 8 pounds of plaster material dissolved from a 20,000 gallon pool is not significant and would barely be seen under magnification.  If stains are removed that improve the aesthetic appearance of older pools, then that can be an acceptable program.  If the acid process only removes dirt and scale deposits and not calcium from the plaster itself, well, all-the-better. 

Some new white plaster pools develop a blotchy and darkened gray mottling discoloration within a few months of plastering.  Also, some new dark colored plaster pools develop a whitish and streaky discoloration soon after plastering. 

Those issues are often caused by improper plastering practices.  The chemical start-up program (performed by the pool owner or service tech) may not be at issue, but is often (incorrectly) blamed by the pool builder or plasterer. A no drain acid treatment generally does not properly resolve these type of plaster discoloration defects. Sometimes, the discoloration disappears for a few weeks, but soon returns afterwards. 

Unfortunately, representatives of the National Plasterers Council (NPC) often promote the Zero Alkalinity (No Drain Acid Bath) program as a “solution” for the above problems. But making matters worse, they advise adding 10 gallons of acid to 20,000 gallons of pool water, more than double the amount needed to reduce the alkalinity to zero ppm. That excessive amount of acid added can lower the pH to below 3.5, lower the LSI to a negative (-) 5.0, and dissolve about 20 pounds of plaster material from the surface.  (Twenty pounds of plaster material is equivalent to 120 ppm of calcium carbonate dissolved from a plaster surface which then increases the calcium hardness of the pool water).

And if adding all that acid doesn’t improve the appearance of the plaster well enough, amazingly, they advise to double the dose of acid for another week!  It removes about 40 pounds of plaster material! That treatment is absolutely detrimental to the plaster surface, and a disservice to the pool owner. It even destroys the evidence of the real cause of the plaster discoloration defect! 

That type of acid treatment causes an severely etched plaster surface that was originally smooth, which will then begin to stain easier and sooner by dirt and metals in the water after the acid treatment program has been performed.  When the pool becomes stained and aged within a year after a Zero Alkalinity treatment, who is going to be blamed?  Unfortunately, whoever is maintaining the pool water chemistry, not the plasterer.

To further undermine pool owners and service techs, the plaster industry advocates that pool water with a slightly negative LSI (-0.1 to -0.3, which is within APSP standards), is detrimental and that it will cause everything from craze cracking to gray mottling to plaster spalling (delamination). Yes, even the same gray discoloration that the so-called Zero Alkalinity process attempts to remove.  Obviously, that is contradictory and completely false.  No wonder they claim that pool plaster will only last about 7 years. But the fact is plaster will last 20 years if plastered with good workmanship and maintained properly.

That agenda enables plasterers avoid being held responsible, blame water chemistry, and get rewarded with additional work.  This injustice won’t stop until pool builders and other groups confront the plasterers. 

("No Drain Acid Wash" is a trademark of United Chemical Corporation).