Question about lowering PH

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Woodberg

Woodberg

0
Apr 5, 2009
136
Houston, TX (Candlelight Estates)
Current numbers;
FC - 2.5
CC - 0
PH - 7.9
TA - 110
CH - 280
CYA - 40

These were my test results this morning. My pool is only a few months old, so I have been using Trichlor pucks as my main chlorine source while the CYA was rising. I'm thinking its about time to stop doing that. Based on the above numbers I added 104 oz of bleach to get my FC up to 5.

My question is what to do with the PH and TA.

From looking at the pool calculator, if I switch to using bleach, then I need to lower my TA to 70-90. Obviously my PH is a little high and also needs to be lowered. Based on the Pool calculator, I need to add about 18oz of Muriatic acid to lower my PH to 7.6. I think I read that adding acid will also lower the TA, but by how much?

I have a SPA that overflows most of the day so I get a decent amount of aeration. I think this is part of the reason why my PH continues to rise.
 
ideliver has got you covered. When you add the calculated amount of acid, your TA will drop along with it your pH. Then, unless you have other issues down the road (rapidly rising pH), just leave your TA alone.
 
Woodberg said:
How long does it take for the acid to take effect? I checked after 1 hour and the FC level had risen to 5, but the PH, didn't look like it had changed much. You might give it another hour but I suspect you'll need to add more.....mine usually changes in 30 minutes.

Is there a way to know how much the TA will drop when adding acid? No, I don't think so. Even the pH change is a little inexact but you'll stay well within acceptable parameters
Click to expand...
 
The amount of change in TA from the amount of acid needed to lower you pH from 7.9 to 7.6 is going to be less than the precision of the TA test!
If you want to lower your TA a bit I would suggest that when you add acid to lower the pH lower it ot 7.0. It will rise on its own over time and each time you do this you will take a bite out of your TA. Once your TA is at target then only add enough acid to lower the pH to normal levels when it rises too high.
 
Woodberg said:
Is there a way to know how much the TA will drop when adding acid?
Click to expand...

Yes, my Pool Calculator can tell you that. Take a look at the effects of adding chemicals section down near the bottom. The PH calculations in that section are very approximate, but the TA calculations are quite accurate.
 
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