Calcium precipitating out of solution

[BPKlein]

Good Afternnon,

We have been maintaining our pool via the TFP methods for many years. We have not had ANY problems to speak of in several years.

This summer, I think we see some calcium precipitate on the pool walls. It reminds me of a saltwater aquarium that is run with the TA or Calcium too high and leaves a white powder on the glass. In our case, we have a white, powdery substance that is sticking to the walls. From the surface, it appears to slightly discolor the walls of the pool. Vigorous rubbing with your hand, or aggressively brushing with a nylon pool brush will release a white powder that almost instantly dissolves in water.

The pool is chlorinated with a SWG. Because of this, the pH constantly needs attention. It takes about a week for the pH to rise to 8.2. The addition of 1-1.25 gallons of muriatic acid brings the pH down to 7.2-7.4. We are trying, slowly, to bring the TA down some, and see if the pH swings are less.

Here are the numbers....
FC 8-9
pH 7.5 (today)
TA 90
CH 425
CYA 80
Salt 3180
BOR 15
Temp 88
CSI .04 (today)

Other than appearance, is this something to worry about?

ThankYou,
Bryan

 

[Texas Splash]

Bryan, you have the right idea. Just keep working on the pH/TA factor. If you lower the TA just a little more (say 60-70) it should help with two things: 1 - helping to slow the rate of pH increase; 2 - lower your CSI a little. If you can keep the CSI slightly negative (zero to about -0.3) that should help prevent the calcium from trying to find a home on your walls of SWG plates.

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.

www.troublefreepool.com

 

[mknauss]

I would suggest controlling pH a bit better. When you let it rise above 8, your CSI is in the scaling region. Lower it to 7.4 when it rises to 8. Adding acid every 3-4 days would work better. Or, spend an afternoon and lower your TA more aggressively.

 

[BPKlein]

TexasSplash, ThankYou. You mention SWG plates....they are spotless and never have been cleaned. They are in summer number 4.

mknauss, It should be easy for us to divide up the acid additions. You mention “an afternoon” to move the TA down. What would that look like? I know lowering pH to 7.2 and aerate. But, how high should the pH come up, before it is pushed down again?

 

[mknauss]

With your pool volume you would need some serious aeration.

When the pH hits 7.5, drop it to 7 or 7.2. With lots of aeration, you can get the TA to drop 10-20 ppm fairly quickly.

I suspect your fill water TA is high? Than can create issues when you add water due to evaporation.

 

[BPKlein]

Our fill water is actually pretty low in TA. We just haven’t been aggressive to try and bring the TA down. With several decorative sprayers, the SWG and a Polaris 280 that can be trapped on the surface (somehow), I think we can get pretty aggressive with the aeration.

 

[mknauss]

Our fill water is actually pretty low in TA.

Interesting. Why is your TA at 90ppm then?

 

[BPKlein]

Looking back in my pool math app, our TA has been at 90 for more than 2 years.

 

[mknauss]

Then you are adding alkalinity or your fill water TA is at least 50+ ppm.

 

[BPKlein]

I can test again, but I don’t remember it being high.

The only thing we have added in 2 years has been CYA and acid.