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Thread: PH, TA, CH relationship questions

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    bbrock's Avatar
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    PH, TA, CH relationship questions

    Couple of things, Richard320, I have not checked on "Effects of Adding Chemicals" section of Pool Math, but wouldn't the Cal-Hypo add other things and affect the pH or TA, despite it raising CH as you stated?

    Jason, can you explain/expand your statement "It is best to be careful to always keep the PH below 8.0." Why? If a person SLAMs his/her pool, then it can be assumed that during that time the pH may rise to > or = 8.0, even if it was lowered prior to the SLAM. What then?

    "When CH is at the low end of the range, it is best to keep TA in the upper half of it's range to balance things out." Yes, it is an inverse relationship, right? I have found that with my pool (in Northern CA with high CH fill water) that I have a high CH 1000, but a low normal TA 60, which balances things out. This seems to be the natural effect/progression of the pool water. The water is balanced and has a stable CSI. Using Pool Math, one can play with the numbers and increase/decrease the CH or TA to see how that will affect the CSI. In this case, when I increase or decrease them both, it negatively affects the CSI and the water is unbalanced, but when they are inverse the CSI is balanced.
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    Re: When do CH and TA levels warrant adjusting?

    Cal-Hypo is very much like bleach or chlorinating liquid in its effects EXCEPT that it additionally increases Calcium Hardness (CH). For every 10 ppm Free Chlorine (FC) added by Cal-Hypo, it also increases CH by at least 7 ppm. The effects on pH and TA from Cal-Hypo are virtually the same as from bleach or chlorinating liquid.

    We often recommend that one lowers the pH before a SLAM if that SLAM is going to be using a lot of chlorine (such as with higher CYA levels).
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    JasonLion's Avatar
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    Re: When do CH and TA levels warrant adjusting?

    High PH significantly increases the risk of metal stains and calcium scaling. The 8.0 cutoff assumes you are generally following our recommendations, which include ignoring the PH measurement while SLAMing. If you want to get technical the actual high PH cutoff varies somewhat depending on the details of the situation, but when following our recommendations it is almost always somewhere around 8.0.

    Fill water CH at 1,000 is an extreme situation, which falls outside our general recommendations. When CH is very high, you want to keep both PH and TA low to compensate, and you can use the CSI calculator to help you figure out just how low. In this situation the PH below 8.0 recommendation would not apply. Instead you would likely need to keep PH well below 8.0.
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    bbrock's Avatar
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    Re: PH, TA, CH relationship questions

    Tx you two.

    Sorry I wa not more clear. My current CH is 1000. And, I have high CH fill water, but I don't think it is at 1000. I tested a very long while back, but if I recall it was somewhere b/w 300-400.
    19k gal IG plaster, built '70s, probably resurfaced in '80s-'90s; Blue Haven Hayward filter C4520BHMB (Filbur FC-1275 cartridges); Hayward MaxFlo sp2302 VSP 1.5hp; 6 solar panels 288. sq. ft. total (142"x47.5" ea.) on 1 story hm; Pentair Compool LX220 Solar Controller; FlowVis flow meter; Maytronics Dolphin S200; AG 300 gal AquaTerra spa; TF-100 & Speedstir; gone: Pentair Challenger 3/4 HP 1 speed; Polaris 280

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