High pH, normal TA, adding acid doesn't decrease pH

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
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My Pool: 26,000 gallon, freshwater, plaster, kidney shaped, variable speed pump, DE filter

High pH, normal TA, adding acid doesn't decrease pH

Postby jamescookmd » Sun 27 Nov, 2016 19:12

I'm adding lots of muriatic acid to my pool and the pH doesn't change.

pH 7.9, FC 4 ppm, TC 4 ppm, TA 100 per Taylor test kit.
pH 7.9 per electronic pH probe

Estimated 26,000 gallon pool. Per the "acid demand" steps in the test kit adding 2 liters of 20 baume muriatic acid should drop my pH to 7.5-ish. But I've added 2 liters several times over the last few weeks and I don't see any change.

Other details: This pool was replastered 1 year ago. At the time the pH kept increasing (probably due to the plaster curing) and I was able to control the pH with acid. Likewise this summer the pH slowly crept up and I could keep it down with acid. But since this winter I can't get the pH to drop at all.

I live in northern California. Air temperatures are 60ish degrees during the day, 40ish at night. The water is around 55 degrees.

I usually add the acid by pouring it directly out of the bottle as I move along the edge of the pool. I don't dump it all in one place. I've tried adding in the deep end and near the jets. I don't put it in the skimmer since that's supposed to damage the pump. I usually retest the pH the day after adding acid. I've got a variable speed / low flow pump that I run for 4 hours at low speed + 2 hours at high speed for the pool vacuum robot.

Any ideas what's happening here? Acid accumulating in the deep end of the pool where I can't measure it? Why did acid work in the summer? Should I increase the amount of acid I'm adding?


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Re: High pH, normal TA, adding acid doesn't decrease pH

Postby Denniswiseman » Mon 28 Nov, 2016 05:22

Hi James
A few questions
How do you chlorinate? A SWG tends to raise the pH
Do you have a waterfall or other form of aeration which raise's pH?
Does the TA reduce as well as the pH with the addition of MA (I tend to use MA to reduce TA and aeration to raise pH after adding it)
When adding MA it's best to pour in slowly over a return jet and then brush the pool to disperse it
If all else fails add more MA raise the chlorine level and winterise

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