Acid Question

[Miniduper]

I'm beginning the process of trying to lower TA. Plan is to add 2 Cups of 14.5% Muriatic Acid to bring pH down to 7.2. Then I have the return pointed upwards aerating, wait for pH to raise back to 7.8 and repeat until TA is 90. How long should I wait between re-testing pH and adding more acid?

Current Numbers
FC 7.5
pH 7.8
TA 180
CYA 42

 

[Richard320]

There are too many variables to predict. A lot depends on how vigorous the aeration is. If I set my spa to max churning, I can move pH all the way up in an hour. But it looks like it's boiling. For you, start at two hours and see how much it's moved, then check again based on that. Maybe you'll need adjusting and maybe you'll decide it needs four more hours. Who knows? But do understand that as TA drops, pH rise slows. So if it pops up in two hours the first time, it may take 2:20 the second, and 3 hours the third.

 

[Chasarms]

When my TA was at 140, pH would climb from 7.2 back to 7.8 in 5-7 days with only natural aeration. I would check it every other day at first. As TA comes down, the time between MA additions will increase.