TA, Ch, Ph and CSI control

[Mike0893]

I have recently added a Circupool RJ60 to my pool. It works as advertised and I am happy with it. But the last couple of times I emptied my pool cleaner i noticed some whiteish sandy looking crystals in the basket. I googled this and think this is being caused by my CSI having reached into positive numbers on occasion. So now I'm trying to keep my CSI into negative numbers only. That leaves me with a pretty narrow band for the PH of 7.6 to 7.4. I generally have to add 1/2" of water to the pool every day and I know the TA of my fill water is very high (300). This of course causes the PH to rise. Another factor is that the temperature of the pool can vary by 7 degrees or more in a single day depending on how hot it is outside. I have the max temp set to 87. So my question if there is anything I can do to better control my TA, CSI, and PH. I can't seem to get the TA to lower very far because I can't add too much acid or the CSI will go below -3. Any suggestions would be appreciated.
Latest Test
FC - 8
Ph - 7.6
TA - 80
CH - 420
CYA - 70
Salt - 3400
Temp Today 82
CSI -.12

 

[ajw22]

Get your TA down around 60.

If your CSI gets low while you are lowering your TA that is OK. A low CSI does not do immediate damage. It takes a low CSI for months to do damage.

From TA - Further Reading

Why Should TA be Lowered with a SWG?​

Usually a TA on the high end is fine if the pH is stable. However TA does need to be adjusted down with an SWG. The problem is, INSIDE the cell, the CSI is very different than in bulk pool water.

With high TA and aeration from the bubbles the SWG creates, you'll get faster pH rise inside the cell and so there's more potential for scaling. With current reversal, the cell tends to stay clean but you'll get more snowflakes out of the returns. Calcium hardness is only one part of the equation.

If the SWG cell pH rises much above 10 (and it can easily do that) and if there is sufficient levels of carbonate ions available (CO3--), then you will get calcium carbonate precipitation. The higher the TA and pH, the more carbonate anions are available.

Borates are particularly helpful preventing scale in a SWG because the pKa for boric acid / borate anion buffering is approximately 9. That essentially means you get the maximum buffering capacity at a pH of 9 and that tends to hold down the pH rise inside the cell. Keeping the pH below 10 in the SWG cell reduces the risk of calcium and magnesium scaling (insoluble magnesium hydroxide precipitates at a pH of 10.2 or so).

 

[Mike0893]

That was helpful. I’ll work to get the TA down to 60. I’ll plan on borates too. Thanks