Battling high alkalinity in new pool

[waldreps]

I use bleach or 12.5% liquid chlorine if it's on sale so I don't have to worry about the cal hypo thing. Do you think I should try to keep the ph low while I'm filling the pool or just wait till it's filled?

[PoolDoc]

Actually, if you lower it AS you fill it, and arrange for your fill water to 'splash' into the pool (aerating it) you will strip quite a bit of carbonate alkalinity before you even get it full!

By the way, you do want to follow the "lower it to 7.0, and then add one more dose of acid" method. You test kit almost certainly can't distinguish 5.0 from 6.8, and a pH of 5.0 will damage things. However, if you lower it to the lowest distinguishable level (just above 6.8) you can add one more dose of acid and be pretty sure you haven't gone lower than 6.5.

Ben

[waldreps]

How long after I add the acid should I wait before retesting the pH? I've got about 20,000 gallons in the pool right now and it holds a totally of approximately 28,000 gallons. It's not up to the return nozzle or the skimmer yet so while I have the pump running, the return is just spraying into the pool. I think that should give me some good aeration. I've stopped filling it for now so that I can spend a little time trying to get the alkalinity down. Last night I tested the pH and it was 8.2 which is the highest number on my kit. I guess it could have been higher and off the kit's limits. I added a whole gallon of acid and let the pump run and return spray into the pool all night. I just tested the pH again and it was at 7.8. This time I added a half a gallon of acid. The pump is still running. I want to test it again as soon as I should to keep on top of it. How long after adding the acid should I test the pH again? Thanks.

[PoolDoc]

If you've got it circulating, you can add acid, wait an hour, and then test. If the pH is above 7.4, add more acid. If the pH is BELOW 7.2, wait another hour and test again. What you want to do is cycle the pH below 6.8, but not very much below, and then let it rise.

[waldreps]

Ok, I just went out and tested the pH again and it was 7.5. Hmmmm, I thought it would be lower than that since just two hours ago it was 7.8 and I added a half gallon of acid. I just went ahead and added the other half gallon and will test again in an hour. Looks like I'm going to need a lot of acid.

[PoolDoc]

If you are aerating effectively, you may 'consume' the acid very rapidly indeed. But be careful; as your alkalinity drops, it will take less and less acid to move the pH. You don't want to increase your doses, and then suddenly find you have a pool pH that's testing as 6.8, but is really 4.8!

[waldreps]

Ok, thanks for the warning. What does a pH that low do? Just curious.