Low TA, high pH

[radaklj]

Since the end of summer, my TA has decreased from a range of 90-100 down to 70. My pH is slowing drifting up and is currently 7.9 I am reluctant to add acid in fear of driving the TA so low that I will get in to pH spikes. I suspect the problem may be that I have not added any tap water to my pool since late October (live in southern CA and continually pumping rain water out of my pool) I suspect that rainwater may be lower in alkalinity than tap water.

Should I add sodium bicarbonate to get the TA back up, and then add acid? Or should I wait until the rains are over hence requiring tap water to maintain pool level and see if that corrects the problem? Most recent chemistry from TF-100:

pH 7.9
TA 70
Chlorine 4.0
CYA appromimately 60

Would appreciate any feedback.

Les

 

[Texas Splash]

Good morning Les! I wouldn't raise the TA. 70 is still with the TFP recommended level range, and some folks will even allow it to settle slightly lower as long as their CH isn't extremely low (for CSI/plaster reasons). If you added baking soda now, your pH would probably climb faster. As you control pH with acid, the TA may actually fall to about 60 and allow your pH to remain more constant at say about 7.7-7.8. There's a place we like to call your pool's "happy place" that should be a nice compromise for the two of them.

Hope that helps.

PS - Watch the FC while you're at it. With a CYA of 60, you really don't want to FC to fall below 5.

 

[Patrick_B]

No, if the pH is drifting up a little that is normal. Having acid added with 70 TA should cause no alarm at all and puts you in no danger. Rain or enough of it can lower TA and CH as well since it contains neither. Probably a good thing where you are. Keep the pH at the suggested ranges and see if it stabilizes somewhere near the upper range. Adding enough to drop you to 7.6 or 7.7 wont hurt anything, so no worries. Likely you'll still see it slowly creep upwards. Perfectly normal even in that range.

 

[radaklj]

I appreciate the feedback. I will add acid to get back to the 7.6-7.7 range and monitor the TA. Thanks folks.

Les