CH rising?

[chem geek]

Wow, that's still a lot of acid you've added. 7 ounces every other day would be over 8 cups of acid over the 19 days. Since only about 3 cups would be needed to have the TA lowered by 10 ppm, it could be that the TA test is measuring a little low so it's more like a 15 ppm or so drop. That still only accounts for about half of your pool's acid demand. At least your 24/7 use of the waterfall explains why you have to add acid and see a TA drop. What is still not explained is the additional acid demand and the increase in CH. I'll bet it's the water temperature since you did the test without letting the water get to room temperature. Try doing that the next time(s) you test and let us know if it is still rising.

By the way, it is not necessary for you to keep your pH as low when the water temperature is cold. Natural water balance will have the pH rise from 7.5 to 7.7 when the water temperature drops from 80F to 50F so you could keep your pH at 7.7 to 7.8 and probably need to add a lot less acid to keep the pH there. Your water chemistry would be more in balance at the higher pH, though it's not very far out of balance now (so the main reason to do this is to lower your acid demand since you have to keep the water flowing to prevent freezing).

I still wonder where the extra acid demand is coming from. One drop in a TA test isn't very accurate so perhaps over a longer period of time the results will make more sense.

Richard