In Kim’s blog post on plaster mottling, Mitch Brooks, the Executive Director of the National Plasterers Council, made the comment “We solve issues...not point fingers which is what you guys love to do!” For those of you who have been on the short end of the NPC’s collective finger, or specifically the finger pointed by the NPC’s Technical Director, Greg Garrett, that comment by Mr. Brooks sounds pretty incredible. For those of you who are unaware of the type of finger pointing Mr. Garrett engages in, consider the following:

In April of 2001 Greg Garrett associated what he called “spot etching” and “highlighting” with aggressive water chemistry (pool in Phoenix AZ – see oB-00004). He also specified that there was no responsibility on the plasterer involved. The professional laboratory analysis then showed that the real culprit was the plastering company and its workmanship.


In August of 2003 Greg Garrett associated mottled white discoloration of colored plaster with aggressive water chemistry (pool in Tracy CA – see oB-00005D). He also specified that there was no responsibility on the plasterer involved. The professional laboratory analysis then showed that the real culprit was the plastering company and its workmanship.


In August of 2003 Greg Garrett again associated almost total white discoloration with aggressive water chemistry (pool in Livermore CA – see oB-00005E). He also specified that there was no responsibility on the plasterer involved. The professional laboratory analysis then showed that the real culprit was the plastering company and its workmanship.


In August of 2003 Greg Garrett also associated patterned white spotting of colored plaster with aggressive water chemistry (pool in Tracy CA – see oB-00005M). He also specified that there was no responsibility on the plasterer involved. The professional laboratory analysis then showed that the real culprit was the plastering company and its workmanship.


In December of 1994 Greg Garrett associated spot etching with aggressive water chemistry (pool in Phoenix AZ – see oB-00019). He also specified that there was no responsibility on the plasterer involved. The professional laboratory analysis then showed that the real culprit was the plastering company and its workmanship.


In August of 2007 Greg Garrett associated “etching, highlighting, and associated discoloration” with aggressive water chemistry (pool in Highland CA – see oB-00040). He also specified that there was no evidence of improper workmanship on the part of the plasterer involved… even though the plaster had delamination and cracking though which the gunite could be seen beneath, and the plaster subsequently began to literally fall of the side of the pool! The professional laboratory analysis showed that there was no evidence of any etching. Of course the real problem – massive delamination – was indeed a result of substandard workmanship on the part of the plastering company.


In September of 2009 Greg Garrett associated mottling discoloration with aggressive water chemistry (pool in Tarzana CA – see oB-00044). He also specified that there was no responsibility on the plasterer involved. The professional laboratory analysis then showed that the real culprit was the plastering company and its workmanship.


This is just the tip of the iceberg. I have only included examples of pools where I have both written evidence of Mr. Garrett’s statements and a professional failure analysis lab making a determination on the same pool. But Mr. Garrett is making a cottage industry of visiting pools and blaming water chemistry when the actual causes are known mixing, placement and curing defects documented in conventional cement/concrete science. I have read many, many more reports written by Mr. Garrett that are along the same lines.

In many of these cases, Mr. Garrett was involved specifically on the recommendation of the National Plasterers Council. He is, after all, their Technical Director. But keep in mind that this isn’t just a pattern of making incorrect assessments – these are real pools where real pool owners and/or service techs were put at risk for replastering pools when the fault lay with the plastering contractor.

Now, I understand that Mr. Garrett, as well as onBalance partners, specifically visit pools where the whole point is to make a determination as to causation and responsibility. But it has always been our understanding that such determinations should be based on fact and science, rather than apologetics.

Feel free to click on the links in this blog and see the comparison between onBalance determinations and Mr. Garrett’s. I hope these examples illustrate the absurdity of Mr. Brooks’ claim that it is onBalance that is “pointing fingers.”

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  • Scott - thanks for the comment.
    Your #1 - Been there / seen that, athough here it is either water-dipped sponges or long horse-hair brushes...
    Your #2 - Not sure if I've seen that. Certainly on older pools, but I don't think I've come across that on a new pool. However, varying thicknesses of new plaster can hydrate at different rates, resulting in mottling...
    Your #3 - Not sure I get this one? I don't have personal experience with it since we don't add base chems to new plaster pools here, the water is usually well over 8 at startup (unless bicarb started...) and we add acids, not bases...
  • My observations of pools which suffer from extensive mottling.

    1) Plaster contractor has a small crew and gets behind when the plaster goes off. In order to keep the plaster "alive" out come the squirt bottles. This leads to an alteration of the cement to water ration in a localized area or washed out paste.
    2) Plaster was placed on the shell at less than 1/2 inch thus allowing for gray structural color to shine through.
    3) Chemicals (specifically extremely basic ones) were added immediately following the pool being filled and allowed to rest on the bottom of the pool without dissolved thoroughly.
  • Well, since I did not do the in pool acid wash, I may be wrong (don't tell my wife!) but I was pretty sure that I heard 0 pH! The pool company dumped in 1 gallon of acid for every 1,000 gallons of water and set a pump. I realize that would lower both pH and TA, but I believe that they were shooting for a 0 pH.

    I started another thread to not dilute the original post here. Maybe I should have thought of that the first time!
  • Did you maybe mean 0 alkalinity (pH 4.6) rather than 0 pH? A pH of 0 is almost impossible to achieve in a swimming pool, but 0 alkalinity is an accepted stain removal technique...
  • I didn't mean to hijack the thread! Maybe I should just start another thread instead!

    I followed a 0 pH in pool acid wash a couple of months back on a PebbleSheen pool. So much CH on the floor that you almost couldn't see the black P-Sheen anymore! After the 0 pH we came in and pulled the CH out to 50 ppm (we ran it a little low, so we added calcium chloride to bring it back up in range!). The pool looked absolutely gorgeous, which I expect from P-Sheen, but I would not try it with plaster!

    If time is on the customers side, and if I could give them back 150-ish CH and they kept the pH low, then it sounds like an option without being overly aggressive, correct?

    I'll try and start another post on the issue so as not to blur this any farther than I have already!
  • Stain removal is a whole 'nuther ball game from the subject of this blog, which was dealing with chemistry vs. workmanship in various plaster defects. Not that there is anything wrong with your question, it’s just that the background info for your answer isn't here in this blog.

    The LSI of your parameters, -0.9, is aggressive enough that there will be a tendency to dissolve calcium carbonate. But not at anywhere near the rate you would achieve with, for instance, a No-Dran acid wash like United Chemical introduced. In their process, acid is added until you have a pH of 4.5 and an alkalinity of 0, which produces an LSI of less than -4.0 (on a logarithmic scale!). And even at that level of aggressivity, their process takes days to weeks. So although you will likely dissolve calcium carbonate in your scenario, it will likely be a long slow process. (That is something we could replicate in our lab and measure, if it came to that...) I don’t know if your customer is comfortable with that or not. And you would need to make sure and rebalance when the scale was gone, or the plaster paste will be next.

    I share your dislike of traditional acid washes, but I have had excellent results with the No-Dran process, with Jack’s Magic’s Stain Solution #2, and even more so with wet sanding a pool surface. None of those processes is as invasive as the traditional acid wash.
  • I just got back from another potential job, where they requested an acid wash. As is typical, I declined to do it, as I believe that acid washes degrade plaster (no matter how well the acid wash is done) and this pool has already been acid washed once. I quit measuring CH at 1,000 as I was getting tired of counting drops!

    Let me ask you guys this: If I were to drop the above mentioned pool to around 150 CH and 700 TDS, and if the homeowner kept their pH in the low 7 range, do you feel that the CH deposited on the plaster (which was in okay shape other than the calcium build up) would come back out into suspension? This pool was about 3,800 TDS, 1,000+ CH, 40 TA and 7.2 pH as measured. Non salt pool.

    I think that I understand water chemistry relatively well, but I am always open to learning things. My desire is to provide only accurate information and honest results. This information helps!
  • Bruce,
    pH represents by far the most influential factor in calculating the Langlier Saturation Index. Changes in calcium hardness will certainly impact the LSI, but not to the extent of each pH point. The potential aggressiveness of a "low" calcium hardness level will be a factor of all the LSI variables.
    But, the simple fact is that aggressive water conditions-of any nature- cannot, and do not create the plaster damages and discolorations as claimed repeatedly by Mr. Garrett. If they did, our industry would never have used acid washes, acid startups on new plaster, no drain style treatments, or any "aggressive treatment". Every acid imbalance would have created such damages-but they don't.
    Yes, aggressive water can uniformly etch plaster surfaces, with the degree of etching being a function of the degree of acidity, the length of time the plaster is immersed in aggressive water, and the durability and quality of the plaster itself. Mr. Garrett contradicts himself routinely by claiming an aggressive water condition caused a problem,but then recommending more aggressive treatments to correct the same problem. It stands to reason that if aggressive waters caused the problem, more aggressive water would only make it worse.
    The prominent cement laboratories-the RJ Lee Group and CTL, who have independently examined failed plasters, are more than capable of recognizing "etching" and the damage it causes. One of the RJ Lee investigators is Neils Thaulow, a world recognized expert on aggressive attacks on cement containing surfaces. These laboratories and experts pinpoint plastering workmanship and materials as the cause of these plaster problems, and not "aggressive waters". As you may have read, however, Mr. Garrett, and the NPC, steadfastly refuse to address why their positions completely contradict these reputable laboratories and experts, as well as the established science of the cement and concrete industries, and frankly, common sense.
    Our industry's consumer, and therefore our industry, is best served when we work constructively and honestly to resolve problems andimprove our products and services. When we adopt and promote self serving agendas, we lose credibility with and damage our consumers, while tarnishing our industry's reputation.
  • Bruce – these are good questions that you raise. There are a number of ways to answer the questions, and the topic deserves a blog post all to itself, but let me at least address the following:
    First, we have to define the term “aggressive” in context. When working with swimming pool water chemistry, we commonly use the Langelier Saturation Index (LSI). What does it tell us? It tells us whether the water is oversaturated (i.e., will calcium dissolved in the water have an active tendency to precipitate out of solution?) or undersaturated (i.e., will the water have an active tendency to dissolve calcium carbonate from contact surfaces?).
    This determination is made by the relative levels of pH, carbonate-species alkalinity, calcium hardness, TDS, and temperature. Since parameters may offset each other, it is entirely possible to “balance” a low pH with high alkalinity and/or calcium hardness. For example, water with a pH of 6.0 can be balanced with a TDS of 500, a temperature of 78F, an alkalinity around 500 and a calcium hardness around 1000. (set the sliders at for a graphic picture…)
    But would that be smart? Not in a pool with metal parts exposed to the water! Extended low pH will corrode metal – which is not an LSI consideration.
    Now slide the calcium hardness down to 75… but note that it can be offset by moving the pH to 7.8 and the alkalinity to 150.
    But would that be smart? It is like walking the edge of a cliff – let the pH drop slightly to 7.4 and without enough calcium, the LSI swoops down to -0.4.
    So in terms of everyday pool water chemistry, the recommendation is to go ahead and let one parameter offset another… as long as you stay overall within the minimum and maximum recommendations (minimum pH 7.2, TA 60, CH 150, and max pH 7.8, TA 180, and CH 1000). Those minimum/maximum levels take into consideration not only LSI but also metals, sanitizer efficiency, bather comfort, etc. If you need to operate outside those zones, you better know what you are doing, and why.
    Incidentally, one example of an exception to the operating rules is start-up chemistry. When starting up new plaster, being balanced to carbonate is not the issue – because the vulnerable compound in the plaster is calcium hydroxide. Water that is LSI balanced is still aggressive to hydroxide – which is why our bicarb start technique proves superior to traditional starts. The bicarb start process is not aggressive even to hydroxide – it converts it to carbonate in place (the subject of another blog).
  • How about the levels that are being used for aggressiveness in regards to pH and CH? I would assume that pH lower than 7.0 would be considered aggressive (maybe even 7.2), but I have been told that CH has to be 75 or lower to be aggressive. Would you agree with these assumptions?

    I am not "trolling"; I am asking to educate myself better. I am in the water business and want to give my customers back the best water that I am capable of, so my questions are to validate what I am trying to achieve in the field.
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