Is this pH rise normal?


Well-known member
Jun 29, 2017
Augusta Township, Michigan
Hello all,

Due to all the great help on this website, I just finished the easiest/most stress-free summer of pool ownership I've had. Yay! As I get ready to close, I do have one question about my pH.

I spent the first half of the summer running constant tests, then used that information to make adjustments. My chlorine loss was very consistent on a day-to-day basis, so when I ended up doing was adding the same amount on Tuesday, Thursday and Saturday then tested/adjusted everything on Sunday. It worked great.

When testing, I noticed that often my pH was high, right around 8. I would adjust and test again hours later (or even the next day) and it'd be 7.4 or 7.5, but by the following Sunday, it'd be back up at 8. So every Sunday I'd have to add some sodium bisulfate (I use the HTH brand, 92%).

I read that high total alkalinity can cause the pH to drift up, mine is at 90 ppm - this seems to be on the high end of the recommendation for vinyl pools. My CYA is also on the high end, between 50-60. Calcium hardness is normal.

I haven't owned a pool for very long, so I have no idea if this sort of pH drift is normal or if there is something else I should be testing/checking?

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
It's not uncommon for pH to drift-up slightly every few days or so. Chemistry and aeration in the water contibute to pH changes. You also have room to allow the TA to fall a little which may help to slow that pH increase. Continue to manage (lower) the pH with muriatic acid. In time, the TA should also fall. Each pool is different, but you may find a TA of 70 or so works better to control the pH rise. Hope that helps.


Gold Supporter
LifeTime Supporter
TFP Guide
Oct 25, 2015
My pool has been very similar. As Pat mentioned, lowering my TA to the low end helped. Mine runs about 60. I also added borates to help. This seems to have stabilized pH somewhat so the acid additions are less frequent but I use more MA with each addition so total MA use is about the same.