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Gray Mottling Discoloration #2

  • Rating: 4.3 after 6 votes

As discussed in our previous write-up (#1), NPC representatives Greg Garrett and Randy Dukes (incorrectly) claim that improper chemistry startups or aggressive water causes gray (or grey) mottling discolorations in new white plaster swimming pools. We (onBalance) put their theory to some tests. The following is an abbreviated summary from a series of our experiments, and we thank IPSSA for their assistance and financial donations.

New plaster coupons were made. A proper .45 water-to-cement radio was used. Since calcium chloride is known to cause a darker hue of white plaster, none was added. And since late and hard troweling is known to cause the darkening and spotting of cement surfaces, no hard troweling was performed.

One plaster coupon was placed into water that had a low calcium content of 80 ppm, and a slightly aggressive SI of -0.3. After six months, no graying developed.

One coupon was placed in water with a low alkalinity of 50 ppm and a slightly aggressive SI of -0.3. After six months, no graying developed.

One coupon was placed in water that had both low calcium (80 ppm) and low alkalinity (50 ppm) and a moderate aggressive SI of -1.0. After six months, no graying.

One plaster coupon was placed in distilled water (meaning a zero calcium and a zero alkalinity), and a negative SI more than a -4.0. After six months, minor etching was noticed, but no graying.

Mr. Garrett has also cited high cyanuric acid levels as a cause of graying (NPC October 31, 2007 Newsletter). He references the Arch Study and others to support his position, yet interestingly, those studies don’t mention anything about gray mottling discoloration.

Based on Garrett’s claim, one coupon was placed in water that had 150 ppm of cyanuric acid and another one was placed in 300 ppm of cyanuric acid, each with a SI of -0.3. The water in these two tanks was also periodically (about every two weeks) treated with 10 ppm of chlorine. After six months, no graying of either coupon.

There is general agreement that acid startups don’t result in gray mottling discoloration. Additionally, service techs have noted that new plaster pools filled with balanced tap water has occasionally resulted in gray mottling. This is further evidence that water chemistry has nothing to do with this type of discoloration. And when plaster coupons were made with calcium chloride added, graying was evident.

As mentioned before, both Greg Garrett and Randy Dukes contradict their claim by recommending a “zero alkalinity (aggressive water) procedure for 7 days to remove graying discoloration, even though aggressive water is what (according to them) caused the graying in the first place. In addition, their formula of adding one gallon of acid for every 2,000 gallons of water actually results in adding 2.5 times the amount of acid needed to reduce a total alkalinity of 100 ppm to zero.

Interestingly, Randy Dukes writes in his book “Pool Surfaces Problems and Solutions” 7th Edition 2005, that if the acid treatment doesn’t work to remove the gray, then double the dosage of acid. That is far more aggressive than doing a Zero Alkalinity process. This method, he says, “will usually drive up the calcium hardness up to scaling levels 400 ppm to 600 ppm as the graying (or “hydration” as he often calls it) disappears, so dilute the calcium hardness with fresh water before rebalancing the pool.” Is it really okay to subject the plaster to such an extreme condition that it etches that much calcium from the surface – and should one really expect this to still improve the appearance?

Yet, when it comes to maintenance chemistry, both Mr. Dukes and Mr. Garrett tell service techs that aggressive water is bad for the plaster and that it causes gray mottling discoloration. Incredible!

In summation, there is no study or documentation showing that aggressive water causes gray mottling discoloration in new white plaster pools. We challenge Mr. Garrett and Mr. Dukes to provide the documentation and science proving their claim. Until then, they should discontinue blaming “out-of-balance” water chemistry for this plaster discoloration defect. The NPC should put a stop to this unfair victimization of innocent service techs, and promote unity with the service segment of our industry.

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Comment by Kim Skinner on December 17, 2012 at 1:42pm

For those who read this blog which is now over two years old, note that there has been no response, no explanation, and no study provided by the NPC leadership or their technical advisors which supports their claim that improper water chemistry causes a smooth, darkened, blotchy, gray discoloration in white plaster.  

Also, there has not been any evidence or data provided that refutes the results of the plaster experiments mentioned in this blog above. 

Comment by Que Hales on September 30, 2010 at 10:27am
It appears that Mr. Brooks doesn’t appreciate my tone. Through past experience, I interpret this kind of comment from him to mean he doesn’t like someone asking direct, specific questions for which he has no answer, or which he does not want to answer. I find no rudeness or impropriety in the questions or statements included in my previous comment. And I only find misdirection in Mr. Brooks’ response. Please note that he continues his pattern of not actually answering any of the questions. This has been NPC practice since the turn of the century, when the NPC cleared their Board and committees of dissenting opinions and science in favor of apologetics.
Please keep in mind that for a decade we donated our time and funds to be active members of the NPC as well as active participants in its Research and Tech Manual Committees – that was evidence of our goodwill and tone. We had great, productive experiences and associations up until a faction of the NPC decided they did not want our input.
As far as my caution that service technicians avoid going to the NPC for answers, because they will often be directed to Mr. Greg Garrett, who has a history of incorrectly blaming water chemistry when poor plastering was actually to blame, my answer is too long and involved for a mere comment on this thread, so please take a look at my blog post dedicated specifically to that subject.
Again, my “tone” is one of concern – for the pool owners and service technicians being harmed by the NPC’s activities. Is Mitch concerned? If he was, as the official representative of the NPC, I think he would jump at the opportunity to openly address what he feels we are wrong about.
Comment by Chip Bury on September 17, 2010 at 10:18am
This is a great discussion on research. It appears that there is plenty of evidence indicating changes to the plastering process that can be made to provide a more durable and consistent product. This benefits us all but mainly the consumer. I look forward to the NPC response as they are the ones that can pass this valuable research information to their members to help produce a better product, lower their liability and reduce warranty claims.
Comment by Lyle Watson on September 17, 2010 at 9:35am
By fiberglass do you mean glass finish over concrete or the big bath tub pools?
Comment by Tim Coleman on September 17, 2010 at 3:15am
Gentleman All,

In reading over this discussion I am dissolutioned by professionals who wish to point fingers as opposed to resolving an issue that has long plagued our industry. I personally am not pro or con either the NPC or OnBalance. I am just a dumb pool guy disgusted with what my plaster contractors call hydration or mottling and whom throw up their collective hands as they go off to the bank with my and my clients money.

What is very apparent to me is that fiberglass has made huge inroads into the concrete industry because they can easily point to plaster as a easily identifiable finish problem. The fiberglass guys are working together to bash plaster and concrete pools and what are the concrete pools guys doing but throwing their hands up in the air or pointing fingers at each other. When are we as concrete pool guys going to realize that our industry is dying because we would rather argue with each other instead of working together to protect and promote the very best type of pool available.

Come on guys, work together to resolve this issue for all of us before fiberglass ruins the the aesthetics provided by a concrete pool and many of us concrete builders are gone because we squabbled over something as simple as chemistry and plaster. I for one have started offering fiberglass because it is an easier sell and puts food on the table for the family.
Comment by David Rockwell on September 16, 2010 at 7:57pm
Is there a good reason why can't they respond here? It seems as if we have the start of a great discussion on the topic already. As a pool service man for fifteen years & a construction & renovation contractor for the last seven, I have been following this topic for some time with great interest. My only stake in this debate is how to work with my plasterer & service people to create the best result possible for my clients. Last winter I personally started up a pool using the NPC's guidelines as published on the website, visied the pool every day for the first 2 weeks and 3 times a week for the following 2 weeks. The chemistry was maintained within + or - 0.1. By the 3rd week, the plaster showed a pattern of graying similar to the top photo in Mr. Skinner's post. All I want is to find out why.
Comment by Kim Skinner on September 15, 2010 at 7:43pm
Mitch, as Executive Director of the NPC, you stated that onBalance is incorrect about gray discoloration. I believe you owe the pool industry and PGN members the courtesy to state what the official NPC position is on “graying” and specifically state what you claim we are incorrect about. Industry people should not have to make several phone calls to you and your consultants to obtain this information. Additionally, if the NPC has any study or documentation that aggressive water causes gray discoloration of plaster (cement), you should also provide on PGN, the reference and page number (or a link), so all can review it. It is our belief that it doesn't exist.

And while we are at it, there are several other issues that are outstanding, that the NPC has never responded to. Please also provide the documentation that proves aggressive water causes spalling (flaking), calcium nodules, white spotting, delaminations, and craze cracking.

For seven years, we (onBalance) and other industry members have been requesting information and answers from the NPC on these various issues. It is past time to be forthcoming.
Comment by Jerry Wallace on September 15, 2010 at 6:46am
That is a tremendous offer Rex! If this is pulled off and the event well publicized, I believe that it would be extremely highly viewed! It is an excellent opportunity for both sides to make their case and to be questioned on the merits of their positions for all to see and hear. In my opinion, this is the only way for members of the industry to get a clear perspective of issues like this! Great Job!!
Comment by Rex Richard on September 14, 2010 at 6:02pm
Mitch, please invite Greg Garrett or any other representative to provide information supporting your position to join us either here or in a debate forum. They are truly welcome as it is the sincere interest of this site to inform the industry and dispel the many myths that have plagued our industry for so long.
Comment by Rex Richard on September 14, 2010 at 5:57pm
Thank you Jerry... indeed open discussion will always benefit the truth. The Pool Genius Network formally extends an invitation to both the NPC and onBalance to provide a public, live, video streamed, forum, with a live interactive question and answer chat, configured to correspond in real time with the presentation.

We have all the equipment for video capture and live streaming and will provide the service at no charge. If there is an interest in bringing the science behind this discussion to light we will be glad to host the discussion. Feel free to contact me to arrange the details.

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