High ph


New member
Jun 12, 2007
I've had this pool for over 20 years. Re-built it 4 years ago with pebble-sheen, new tile and coping. I've fought pH forever. Getting scale on the tiles. Installed a SWG 2 years ago as well. Pool has built in spa, non-heated, just bubbles. Pool is crystal clear. Sand filter.

pH: 8.4 (guess, over test kit range)
Alk: 170
Cal: 260
Cya: 30
Temp: 86
Salt: 3600
FC: 17 (just super shocked due to black algae) Clorox

I just added 16 oz of Muriatic Acid this morning, will check the pH tomorrow. By the way how long to let acid work before re-testing?

I think I know how to lower pH but it never stays low. Any input out there?

The SWG can't keep enough Cl in the pool so I think I need to raise the CYA to about 70-80. I'm worried about that as I did pucks for years and cya got out of bounds.

But in Central TX, sun eats a lot of Cl.

Pool size 13500 gal.


Mar 14, 2010
First suggestion is go to pool school and read and re read. The pool school link is in the upper right hand corner of the page. Seems to me that the alkalinity is a bit high. Also the pool calculator might be helpful in determining how to bring levels where you want them. Good luck. Others will be along soon who are more knowledgeable.


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
You need to get the pH down, and keep adding acid to keep it down. By dropping pH to roughly 7.2 then aerating it well, you will lower TA and raise pH back up. Then you repeat. And keep repeating until the TA gets down to 80 +/-.
Once TA is lowered (and adding water will tend to push it up) pH rises slower.

Pool Calculator says you need better than 2 qts ofto get pH down to 7.2. This will also lower TA about 20 ppm. You have a long way to go to bring it down from 170! You can retest pH within hours of adding acid, as long as the water is circulating well.


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
With an FC of 17, the pH test in most all kits is invalid. If you're testing with a Taylor kit, the pH test is fairly reliable up to about 10ppmFC.

I'm not sure about other brands but, nevertheless, you will need to let your FC get down to around 5ppm or so and then do a pH test before you make any adjustments.


TFP Expert
LifeTime Supporter
May 30, 2007
South Carolina
Yep, you need to get the high pH under control before you resume shocking.
As Dave said, allow the FC to drop below 10 and then test and adjust your pH down to about 7.2.

Your CYA of 30 is nice for shocking, but too low for a SWG system.
I suggest you leave your CYA where it is until you are done shocking.

Welcome to the forum :wave:


New member
Jun 12, 2007
Thanks for the input. I'm using Ben's test kit with the titration method of FC. I will continue adding acid until I get the pH under control. I am cautious of adding acid too quickly. Will ad 16 oz more tonight.

Once I get the pH under control and the TA back down shoulld I raise the CYA to about 60-80.



TFP Expert
LifeTime Supporter
Feb 23, 2008
Denton, TX
rkted said:
I am cautious of adding acid too quickly. Will ad 16 oz more tonight.
Don't add any acid until your FC is at 10 or below. The pH can read falsely high in high FC environments. Let the FC fall to below 10, check the pH again, and treat it then if it is still indicated.