Frequency of pH Adjustment

[jereece]

I am using bleach for chlorination and muriatic acid to reduce pH. My question is

1) At what pH do you adjust your pH down
2) How low do you take it when you adjust the pH
3) How frequent do you adjust your pH

I seem to be adjusting mine from 8.0 down to 7.4 about once a week. In past years I don't recall having to adjust it this frequent. Below are my specs.

FC 2.0
TC 2.0
pH 7.8
CYA 30
Alk 80
Ca 20

[Madty]

I think your TA is a little low- this will cause PH to bounce. I'm dealing with this problem now with a SWG and cloudy water. Baking soda, acid, baking soda, acid....

[CarlD]

That's right. Total Alkalinity is kinda mis-named--it's a buffer or stabilizer for pH. You raise it by adding baking soda. Your pH at 7.8 is at the top of the acceptable level--and your chlorine is a lot less effective there than at, say, 7.3, which is also acceptable.

You should raise your Tot Alk to at least 100--and lower your pH to 7.4-7.6. You'll see Tot Alk go down a bit then, but you you can raise some more. 100- 125 is perfect for Tot Alk and your pH shouldn't move so much.

[aquarium]

At PoolDocs sticky on adjusting alkalinity he says:

Also, do NOT try to lower your pH all at once; for all sorts of reasons, it's important to do it gradually!

What would those "all sorts of reasons" be?

I add about two cups of muriatic acid to a 15,000 gallon IG plaster pool every day to keep pH in the mid 7's, but we have very high alkalinity and hardness here. That bumps it down about .2 on the pH scale each time, but it's always creeping up by about the same amount each day. I also add about 4 cups of bleach per day, so that is also pushing the pH higher.

[waterbear]

I think what Ben means is that you don't want to dump a lot of acid in all at once to lower the pH by a lot. It is too easy to overshoot your target! Also it really takes about 24 hours for the pH to stabilze after ajusting it. It is much safe to make a small change and keep doing this over a few days until you get it where you want it and then add just enough acid to keep it there for maintenance.

[aylad]

Just a comment--with a CYA of 30, I'd raise the Cl to at least 3........also, you might be experiencing the rise in pH due to use of bleach for chlorination. Some pools experience this, some don't.

Janet