Re: Gallons of muriatic, days of aeration...
Originally Posted by
Sigrid
Thanks all, here's the latest:
I put in a gallon of muriatic, let it run for 2 hours, got the pH to the light end of 7.2 (using Taylor kit). Just added in 1/3 gallon of muriatic to get it to drop down to the 6.8 range. BUT, before I added additional acid, I measured the alk and it said it was down to 140. Yay, Progress!! The thing is, I had a 130 on Friday morning, and then by Friday evening, it was back to 190, so I don't trust these low numbers that I get. Think I might have some errors in my methodology...
Wehn you lower the pH you shift the buffer system to more carbonic acid (carbon dioxide gas dissoved in water) so when you test TA it will give a lower reading. As the pH rises back up the buffer shifts to more carbonates/bicarbonates so when you test the TA it will test higher since the test will tell you how much alkaline carbonate ions are in the water. This is normal. The idea is to 'gas off' as much of the carbon dioxide gas that is formed by the lowered pH so that when the pH rises less of the alkaline carbonates are formed and your TA is lower. The process CAN take a while.
I appreciate the warning on not going too low on pH--my kit only goes down to 6.8. I'm going to *assume* that I'm there right now and just aerate like crazy tonight so I don't damage anything.
This is why I cautioned to make SMALL additions of acid and test pH once the pH starts moving. It is very easy to overshoot! With a plaster pool it is ok to go to as low as 6.6 according to Ben's sticky on the subject as long as you have an accurate way to test for pH that low (such as a pH meter or the correct indicator solution and comparator for that pH range)
Thanks Everyone for all the helpful info! I'll post again tomorrow w/ the new numbers.
Hope this is helpful!
Retired pool store and commercial pool maintenance guy.
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