Scaling caused by high CYA???

[dmp717200]

2 year old in-ground gunnite pool with diamond brite quartz. Lots of scaling. Cracks were repaired on bottom of pool 2 years ago and they are still bright blue while the rest of the pool isn't, making the repair very noticeable. Builder's rep (and diamond brite rep) came over and said its a result of me using tablets raising the CYA too high, and that we need to do a drain, acid wash, and low alkalinity start up to address it. Does that sound right? I had been using the pool store for water analysis and they always said the CYA was about 60. His test was showing over 100.

Am concerned with draining pool too. Can't that cause the shell to float? They said they would refill it right away, though.

 

[Texas Splash]

Typically, CYA is not related to scaling. That's generally related specifically to the trio of pH, TA, and CH levels. But on the Poolmath calculator I did play around with some of my own test numbers and learned that if I let my CYA go "extremely" high (i.e. 200) then it did in-fact put my CSI in a dangerous (negative) area. That's the problem with pool store testing versus your own testing with a TF-100 or Taylor K-2006. Anything "over" 100 is really unknown and could be MUCH higher unless someone does a dilution method test. Even on a good day pool store tests are usually off. So without knowing what your true values were for ALL tested items, it's difficult to say what caused the color difference.

Best thing to do now is ensure you have your own test kit (i.e. TF-100) and adjust chemicals from there. I would not drain anything yet until I had my own "proper" test kit. From there, you will learn how much water (if any) needs to be drained. If you do need to drain a lot, then we can help you determine how much to drain/replace at one time to help maintain the integrity of your pool shell. Hope this helps.

 

[ping]

High levels of CYA do not cause scaling as Texas pointed out. A combination of high CH, pH, and TA can lead to scaling. The reps saw something out of balanced and blamed it on that, typical of them it seems.

To fix your problem right you need to know the cause and go from there. The first thing that you need is an accurate test kit, TF-100 see my signature, so you can get reliable test numbers. Pool store testing is worth what you paid for it, nothing. With proper water testing you can then keep the water in balance per TFP and prevent any future scaling, ABC's of Pool Water Chemistry.

 

[chiefwej]

As others have said scale is not caused by high CYA. It is caused by other imbalance. If you use chlorine in granulated form you are adding calcium to the pool, that promotes scale. Chlorine pucks add CYA. The chlorine gets used up but the calcium and/or CYA remains and builds up in the water, causing problems. Excess calcium promotes scale, high CYA will cause issues like algae outbreaks that are impossible to control. As long as you use solid forms of chlorine, you will continue to have water imbalance problems. Any solid form of chlorine brings along something you don't want added to the pool, either more CYA, or more calcium.

There are only a couple alternatives (liquid chlorine and SWG).

 

[onBalance]

I am in agreement with the above comments. But my question is; how can scaling (due to chemistry imbalance) occur over the rest of the pool and not over the cracks?

While it isn't stated specifically, it sounds like the quartz plaster also had a "blue pigment" added to the cement/plaster. If so, and the blue color has faded and turned white; then a possible explanation is that the original color pigment isn't holding up. And perhaps a higher quality pigment was used when repairing the cracks. Therefore, is the problem really "scaling" or it is bad material and additives?