Difficulty raising TA

[bcinsd]

Hi. I have a 15K salt water inground pool in SoCal.
My water is crystal clear and I have no algae but I can't ever seem to get TA into acceptable range.
Chlorine levels (free/ total) are about 2/2-3/3.
pH is 7.6
CYA ~50.
TA has been ~40.
Yesterday, I put in a total of 7 lb of baking soda.
Pool filter ran overnight and acid added to bring pH back to 7.6.
TA this AM is 50.

According to the charts I've read, I should have gotten bigger TA boost from this amount of baking soda.
At this rate, (7lbs raising TA by 10), I'd need to add another 35 lbs of baking soda to reach TA ~100.

Does this sound right?
Any advise appreciated.

 

[ajw22]

Why do you want a TA of 100?

A TA of 50-70 is just fine.

If your pH is stable I would leave your TA at 50.

What is the pH and TA of your pool fill water?

What test kit do you use?

 

[bcinsd]

Why do you want a TA of 100?

A TA of 50-70 is just fine.

If your pH is stable I would leave your TA at 50.

What is the pH and TA of your pool fill water?

What test kit do you use?

I read that desired TA for gunite pool is 80-120.
pH is not so stable. Tries to drift upwards. Have to add acid fairly frequently. I've read higher TA helps stabilize pH but not sure if will help to keep pH from rising.

I am using a reagent kit for HD (ph, total/free chlorine/ acid demand/ TA. I also intermittently use dipstick for a quick check and to help verify results. Both kit and dipstick show similar results. Occasional pool store results seem to match what I get at home.

Hadn't thought to check pool fill water. Just did. pH 7.8 TA 90.

Should I just let pool water pH drift up to 7.8?

 

[ajw22]

I read that desired TA for gunite pool is 80-120.

You didn't read that here.

ABCs of Pool Water Chemistry

Recommended Levels

pH is not so stable. Tries to drift upwards. Have to add acid fairly frequently.

pH drift up is normal and natural.

I've read higher TA helps stabilize pH but not sure if will help to keep pH from rising.

You didn't read that here. Lower TA creates less pH rise over time.

TA - Further Reading

www.troublefreepool.com

I am using a reagent kit for HD (ph, total/free chlorine/ acid demand/ TA. I also intermittently use dipstick for a quick check and to help verify results. Both kit and dipstick show similar results. Occasional pool store results seem to match what I get at home.

None of those are very reliable. We recommend you get a proper testkit - Taylor K-2006C or TF Test Kits

Pool Test Kits - Further Reading

www.troublefreepool.com

Should I just let pool water pH drift up to 7.8?

Let the pool find the pH/TA equilibrium. TA 50 or above and pH anywhere in the 7's.

Stop trying to drive either to a specific number.

 

[bcinsd]

Ok Thanks. Love when the answer is to back off, not make more changes. I will let pool drift up to 7.8 and see how it goes. Thanks.

 

[jseyfert3]

I’d just like to add that adding acid will always lower TA. So if you add a bunch of TA increased followed by a bunch of acid you won’t get as much TA increase as you expected.

If you get PoolMath it makes calculating the size of additions easier, instead of using charts. And there is an Effects of Adding section where once the desired amount of acid is calculated to lower the pH other effects like how much the TA will be lowered can be seen.

But as mentioned Ta be pH are very interrelated, don’t try to force the TA to a specific number. And I highly recommend a better test kit.