The concept of the “Zero Alkalinity” process (also known as a No drain Acid Wash) is to make pool water aggressive enough (by adding acid) to dissolve and remove metal stains or calcium scale from cement-based plaster surfaces, including quartz and pebble swimming pools. Unfortunately, this process may remove some of the plaster surface material which is always detrimental in the long run.
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, which results in 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 plaster 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 significantly detrimental and would only be seen under magnification. If the stains are removed and 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, all-the-better.
Sometimes, however, some new white plaster pools develop a smooth, but 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) is not the cause, but is often (incorrectly) blamed by the pool builder or plasterer instead of their own faulty work.
Unfortunately, some plasterers mistakenly promote the Zero Alkalinity program as a “solution” for the above problems. And they also suggest adding 10 gallons of acid to 20,000 gallons of pool water, which is more than double the amount needed to reduce to zero alkalinity. That amount of acid generally lowers the pH to below 3.5, lower the CSI 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). That outcome is significantly detrimental.
Yet, if adding all that acid doesn’t improve the appearance of the plaster well enough, they advise to double the dose of acid for another week! Apparently, they are unaware that that process removes about 40 pounds of plaster material when trying to correct the above plaster defects. That is absolutely detrimental to the plaster surface, it may not work to remove the plaster defect, is a disservice to the pool owner, and it destroys the evidence of the real cause of the plaster defect!
That type of treatment results in an etched surface that was originally smooth, which results in easier dirt and metal staining in the future after the acid program has been performed. When the pool becomes stained and aged within a year after a Zero Alkalinity treatment, who gets blamed? Whoever is maintaining the pool water chemistry, not the plasterer who actually caused the discoloration.
To further undermine pool owners and service techs, the plaster industry advocates that pool water with a slightly negative CSI (-0.1 to -0.3, which is within PHTA 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 it is often claimed that pool plaster will only last about 7 years. But the fact is plaster will last 20 years if plastered and maintained properly.
That misleading agenda enables plasterers to 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 when improper workmanship is evident.
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, which results in 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 plaster 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 significantly detrimental and would only be seen under magnification. If the stains are removed and 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, all-the-better.
Sometimes, however, some new white plaster pools develop a smooth, but 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) is not the cause, but is often (incorrectly) blamed by the pool builder or plasterer instead of their own faulty work.
Unfortunately, some plasterers mistakenly promote the Zero Alkalinity program as a “solution” for the above problems. And they also suggest adding 10 gallons of acid to 20,000 gallons of pool water, which is more than double the amount needed to reduce to zero alkalinity. That amount of acid generally lowers the pH to below 3.5, lower the CSI 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). That outcome is significantly detrimental.
Yet, if adding all that acid doesn’t improve the appearance of the plaster well enough, they advise to double the dose of acid for another week! Apparently, they are unaware that that process removes about 40 pounds of plaster material when trying to correct the above plaster defects. That is absolutely detrimental to the plaster surface, it may not work to remove the plaster defect, is a disservice to the pool owner, and it destroys the evidence of the real cause of the plaster defect!
That type of treatment results in an etched surface that was originally smooth, which results in easier dirt and metal staining in the future after the acid program has been performed. When the pool becomes stained and aged within a year after a Zero Alkalinity treatment, who gets blamed? Whoever is maintaining the pool water chemistry, not the plasterer who actually caused the discoloration.
To further undermine pool owners and service techs, the plaster industry advocates that pool water with a slightly negative CSI (-0.1 to -0.3, which is within PHTA 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 it is often claimed that pool plaster will only last about 7 years. But the fact is plaster will last 20 years if plastered and maintained properly.
That misleading agenda enables plasterers to 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 when improper workmanship is evident.
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