question about TA and pH

[terriolsen]

I had my pool replastered in August 2010.

It has been recommended that I keep my pH between 7.2 to 7.4 in order to avoid white-stuff in my liquidator. To do this, I'm checking my pH every other day and adding between 6 oz to 22 oz (if I missed a day) of acid. So I'm adding acid all the time.... How long before I won't need to keep adding so much acid? I have no water features, no SWG, just plaster that eventually (when?) will stabilize.

I wonder if my frequent acid dosage is what keeps my TA so low. The TA seems to want to be around 80. I keep bumping it up to 100 with baking soda, and then a week or two later, its back to 80. Why is this?

My numbers are:
FC 4.5
CC 0
TC 4.5
pH 7.4
TA 80
CH 400
CYA 30

Thanks!

 

[woodyp]

Dosing it with muriatic acid to knock the PH down also knocks down the TA.

 

[chem geek]

Stop bumping up the TA to 100. Let it drop even to 60. That will lessen the amount of acid you are adding and will reduce the white stuff problem. In fact, with a low enough TA, you won't have to have the pH be quite as low since it's the saturation index that determines the amount of white stuff, not the pH alone. Finally, you might consider using 50 ppm Borates which can also help prevent the white stuff in The Liquidator.