Problem keeping pH in check

[joelans]

Hi - we have a new pool, with a NPT StoneScapes mini pebble finish. It has been opened for about 3 months now. I'm having a really hard time keeping the pH in check. I have to add about 1 quart of Muratic acid (31.45%) almost every day. I can get the pH down to 7.4-7.5 with that, but then the next morning, it will be 7.9-8.0 again. All other readings are fine - Total Alkalinity is about 100 ppm; Calcium hardness is 300 ppm; Free Cl2 is about 3.5 ppm (using a SWG); CYA is about 55 ppm. Filter pump is running about 14 hours/day.

What am I doing wrong? Pool is about 25,000 gallons.

Thanks in advance.

 

[PoolGate]

I am in my 8th season and still adding a gallon a week. It's the nature of plaster.

 

[ajw22]

Welcome to TFP.

Your TA of 100 contributes to your pH rise. The lower your TA the less rapidly your pH will rise.

What is the pH and TA of your fill water?

TA - Further Reading

www.troublefreepool.com

PH TA Relationship - Further Reading

www.troublefreepool.com

 

[joelans]

Welcome to TFP.

Your TA of 100 contributes to your pH rise. The lower your TA the less rapidly your pH will rise.

What is the pH and TA of your fill water?

TA - Further Reading

www.troublefreepool.com

PH TA Relationship - Further Reading

www.troublefreepool.com

Fill water pH 7.5-7.6, TA about 40. I haven't really been filling the pool with any fill water as of late (last fill was about two weeks ago).

I've been trying to keep the TA above 100, since that is what my pool builder told me (they said to keep TA of 100-150 ppm). But, from what I've been reading, that is way too high. It's sounds somewhat oxy-moroic - TA is supposed to buffer pH bounce, so it seems you would want it to be high, but then a higher TA causes faster pH rise.

 

[zea3]

Do you run any water features such as fountains, or have the return jets pointed up to churn the surface of the water? A lot of splashing in the pool? Anything that churns the water contributes to ph rise, along with your TA and new plaster.

 

[PoolGate]

Fill water pH 7.5-7.6, TA about 40. I haven't really been filling the pool with any fill water as of late (last fill was about two weeks ago).

I've been trying to keep the TA above 100, since that is what my pool builder told me (they said to keep TA of 100-150 ppm). But, from what I've been reading, that is way too high. It's sounds somewhat oxy-moroic - TA is supposed to buffer pH bounce, so it seems you would want it to be high, but then a higher TA causes faster pH rise.

T/A = Total Alkalinity - Alkaline being the opposite of Acidic. So the higher the alkalinity, the more acid you need to add. Lowering T/A is basically pre-loading acid in the pool to handle increased alkalinity.

 

[Bperry]

Fill water pH 7.5-7.6, TA about 40. I haven't really been filling the pool with any fill water as of late (last fill was about two weeks ago).

I've been trying to keep the TA above 100, since that is what my pool builder told me (they said to keep TA of 100-150 ppm). But, from what I've been reading, that is way too high. It's sounds somewhat oxy-moroic - TA is supposed to buffer pH bounce, so it seems you would want it to be high, but then a higher TA causes faster pH rise.

That TA recommendation was from when people used trichlor tablets to chlorinate. They are acidic and so they push the pH and TA down over time. With a SWCG, you dont have that push. Ive got new plaster last summer and a couple trichlor tabs in the floater keep my pH very steady when the TA is ~80.

You better get your chlorine up though…

 

[pjt]

I've been trying to keep the TA above 100

How are you testing?

Have you been adding baking soda? If so, stop. TA of 50 or above is fine. A SWCG pool will likely never need baking soda.

Manage the pH with MA and the TA will come down over time. As your TA approaches 50, be judicious with your MA, adding just enough to get the pH into the high 7s.

that is what my pool builder told me (they said to keep TA of 100-150 ppm)

That's bad advice. Disregard it.

 

[joelans]

Well, that fixed it. TA is down to about 65, and it is much easier keeping the pH in check. Thanks to all for your help!