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.