All chemicals in check except acid

jason92s

Well-known member
Nov 19, 2009
57
Sacramento
Pool looks good, I have the test kit I bought from TFP and everything except for my acid level is checking out good. I've been adding about 3/4 of a gallon a week for the past 3 weeks. Yesterday, I added a whole gallon around 6pm, then today I checked it and it's still in the dark purple range of 7.8 to 8.0. My buddy has a similar sized pool (both are salt water if that matters) and he only adds about 1/2 gallon a week. Any ideas on what could be going on? Thank you!
 

jason92s

Well-known member
Nov 19, 2009
57
Sacramento
That's what I thought, but the local pool store said adding 3/4 gallons for 2 weeks then 1 gallon the next week and testing the following day should have lowered the PH by now. Just didn't want to keep adding it if there's something else going on.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
We could give you a much better answer with a full set of water test results. Chances are your TA is really high, which is driving up the PH, but that is just guessing without knowing your actual numbers.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
22,049
San Dimas, CA (LA County)
When I took over the chemicals from the pool service last winter, I was astonished at how much acid I had to add. It took a 10 lb pail of dry acid and another gallon of liquid acid to get the color to change on the test block. And then even more to get it in range. Then there was all the aeration from the spa combined with our brutally hard water in California to use up some more.

It's very similar to doing a drop test, really. You add and add and add and no change then it starts to move and seems like it takes forever, then one magic drop and it all changes at once.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
Your TA level is high, and was presumably much higher before. High TA levels tend to cause the PH to rise, the higher the TA level the faster the PH will rise. Once you get TA down the rate of PH increase will slow dramatically. You should take a look at the How To Lower Total Alkalinity article in Pool School.
 

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
23,371
SouthWest Alabama
Doesn't really have anything to do with pH but your FC is pretty low even for a SWCG. You're asking fo trouble if it stays that low for long.
 

cbad

Member
Jul 13, 2010
12
Your TA is definitely a problem. If you have water features that aerate the water, that could be a contributor as well. Things like spa spillovers, waterfalls, and bubblers all cause the pH to rise.