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

[DONNIE]

I think I have been trying too hard to keep the Ph at 7.5 so every other day when it hits 7.6 I add the 7oz of acid. Last week I wanted to see how high it would go left unadjusted. To my suprise it has remained stable at 7.6 and I haven't had to add any all week. I'll retest the Ch tonight at room temp. Thanks for your advice.

Donnie

[chem geek]

A change in pH from 7.5 to 7.7 might cut down your rate of CO2 outgassing by almost half and cut the acid demand in half, but a change from 7.5 to 7.6 shouldn't be so dramatic as having virtually no pH rise in a week. I'm sure something else has happened coincidentally (maybe something simple like there is less wind). At any rate, the point is that you can live with a higher pH and this will have you add less acid and that is what you are seeing (albeit more extreme than expected).

Richard

[DONNIE]

Can you actually "smell" out-gassing? thought I could smell my pool the other night for the first time.

[chem geek]

Carbon dioxide is odorless so you can't smell it. If you are smelling chlorine, then that is possible (a "clean" chlorine smell unless you have combined chlorine), but I'm not sure why you'd be smelling that now all of a sudden.

Richard

[DONNIE]

Im not even sure it was my pool. Zero CC's. It's been really wet and cold here so Im sure it was just the weather. That or the Opossum thats been hanging around.

Donnie

[CarlD]

I, on the other hand, am baffled by the rising calcium hardness. Nothing you are doing should cause that.

So...Next question: Is your waterfall fiberglass, too, or is it stone and even mortered?