Trying to lower PH slightly but only my TA goes down


Active member
May 14, 2019
Scottsdale, AZ
CYA: 50
FC: 6
CC: 0
CH: 450
PH: 7.6
TA: 80

21,000 gal pebbletec pool. Arizona. Pool water currently about 88° during the day.

A week or so ago my TA was 110, and my PH was 7.6, sometimes 7.7.
I guess PH of 7.6 is "ok", but I was trying to get it to 7.5 or 7.4 - just to see if I could.

So I have been adding muriatic acid 20° Baume, 1 or 2 cups a day as recommended by pool math. But all that seems to happen here is that my TA steadily decreases so it is now at about 80. I don't think I should go lower than this. How do I get PH down without lowering TA?

I'm not really "aerating" the pool per se; although I have a negative edge that runs part time, and an integrated spa we use everyday with therapy jets.


Active member
May 14, 2019
Scottsdale, AZ
With my water hardness (CH 450) and my TA at 80 (lower end of recommended range), a ph of 7.8 would result in a CS value of 0.35 according to pool math app.
As it is, right now with ph 7.6, I have a CSI calculation of 0.16, which is acceptable.

This is why I want a lower ph. And anyway, isn't 7.8 towards the high end of the recommended scale?


Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Any pH in the 7s is fine. High end or low end does not matter.

Any TA down to 60 is ok. Let your pool find the TA and pH level it is happy with. Don’t try and force it to a specific number. You can’t hit both a pH and TA number. Manage the pH and let the TA be wherever it wants.

Monitor your CSI using PoolMath. Any pH and TA combination that gives you a good CSI is ok.