Pool Water Balance is Not (Always) the Problem

onBalance

TFP Expert
LifeTime Supporter
Jul 25, 2011
880
Utah
#1
Pool Water Balance Is Not (Always) the Problem
(For this post, please consider the LSI as being the same as the CSI which is more familiar to TFP members. Pool industry people are more familiar with the LSI).


For 50 years, the pool industry has considered pool water within an LSI (or CSI) of -0.3 and +0.5 to be acceptable and balanced. But recently, and without providing any supporting science or research, the National Plasterers Council is trying to convince the industry that any negative LSI (-0.1 to -0.3) is unacceptable and immediately detrimental to pool plaster. Their theory also suggests that an alkalinity below 80 ppm, or a low calcium level (below 200 ppm) independently as being automatically aggressive even if the LSI is positive.

It is also being claimed that those water conditions cause gray mottling (of white plaster), craze cracking, variable white blotchiness and streaking of colored plaster, random calcium nodules, and plaster flaking (spalling) to occur in just a few weeks or months. That is all nonsense.

Contradictions to Those Claims

Let’s consider that plaster consultants recommend adding 8 to 10 gallons of acid to a 20,000-gallon pool for one week to improve the aesthetic appearance of new plaster finishes, including quartz and pebble. That acid treatment (or acid start-ups, now disingenuously referred to as “hot start-ups” by plasterers) lowers the pH to about 3.5, the alkalinity to a negative number (below zero), and the LSI to -4.0. That water is about 5,000 times more aggressive than an LSI of -0.3. If that type of water doesn’t cause the above plaster issues, how then could water that is 5,000 times less aggressive do that?

Plaster experiments show that those acid treatments dissolve and etch up to 30 pounds of calcium material from the plaster surface and, assuming the surface is relatively of consistent quality, do so uniformly without causing discoloration. (btw, the total weight of plaster material in a 20,000-gallon pool is about 4000 pounds).

In comparison, maintaining an LSI of -0.3 for six months may dissolve about 1.5 pounds of calcium material. In other words, it takes at least 10 years of consistently maintaining an LSI of -0.3 to equal the same uniform etching effect of adding 10 gallons of acid for one week. Note: It is very difficult to constantly maintain a negative LSI because aggressive water seeks to balance itself as it liberates calcium from the plaster surface, and the pH generally rises.

More Contradictions

The NPC/Cal Poly (NPIRC) plaster study was used to mislead the industry regarding aggressive water chemistry. Reviews by two Ph.D. chemists indicated that the (fabricated) conclusions don’t match the results and data. Those studies actually demonstrated that deterioration and spotted discoloration occurred in balanced (non-aggressive) water and in only four months. That implicates poor workmanship or materials as the problem, not aggressive water.

The Portland Cement Association and the American Concrete Institute do not blame rain (aggressive water) for causing rapid discolorations and defects on cement/concrete surfaces. Instead, they have identified improper workmanship and material issues as causes. Rain is about 1,000 times more aggressive than an LSI of -0.3 (which occurs often in pools), and yet, does not cause similar defects or discolorations (as mentioned above) on cement sidewalks and driveways, even after several years.

For many years, thousands of pools across the country have been intentionally (and unintentionally) maintained with slightly aggressive water to prevent calcium scaling, and they do not develop plaster discolorations or defects.

There are petrographic (forensic) plaster studies showing that improper and “short-cut” practices cause plaster discoloration and deterioration problems, some of which only become visible after pools are filled, and sometimes even after months. See this link: Consulting – Pool Help

The Bottom Line

Maintaining slightly aggressive water (LSI or CSI of -0.1 to -0.5) is acceptable. It does not cause rapid plaster deterioration and discolorations problems on quality applied pool plaster. The plaster problems mentioned above are prevented by following good workmanship standards. Right now, there are none. Good plastering standards would provide accountability. That is what my father's plastering business provided to their customers 45 years ago.
 
Last edited:
OP
OP
O

onBalance

TFP Expert
LifeTime Supporter
Jul 25, 2011
880
Utah
#3
The calculation of the CSI uses slightly different numbers than the LSI. The CSI is an upgrade and the more accurate index. But in the end, the difference is minor. I originally wrote this for the pool industry and referred to the LSI which is what they are more familiar with. I forgot to change it for this post. So please consider it being applicable to the CSI that TFP uses. Thanks.
 
Last edited:

kimkats

Mod Squad
LifeTime Supporter
Jul 10, 2012
36,764
Tallahassee, FL
#4
Thank you SO much for this info! This is where I find it hardest to help new pools. The owners have almost no control over who does work on their pools. As such they cannot control the quality of the work done :( If only the PB would make sure the crews they used were willing AND able to do top shelf work.
 
OP
OP
O

onBalance

TFP Expert
LifeTime Supporter
Jul 25, 2011
880
Utah
#9
The NPC's position changed some years ago when the leadership changed hands. Essentially, it was a couple of plaster consultants who make money helping the poor plaster companies get away with poor workmanship, and a couple of plaster company owners who make more money by plastering pools far too fast, that began pushing that agenda about pool water. That became an easy target because several different plaster problems develop after the pool is filled with water. It fools many, even though they have no science, no study that provides any evidence of their claims. Everything points at poor workmanship and materials.

Btw, Congratulations on becoming a TFP guide.
 
Likes: Arizonarob