Can't bring down pH and TA

[jorgeL]

Hello all,

I am using 10% liquid chlorine for sanitation and I add it every week and since my pH (7.8) and TA (125) is higher than I would like I also add 14.5% muriatic acid to bring those down. I thought that I would only had to add acid once and when my pH and TA levels were to a desirable level I wouldn't have to add acid anymore, just weekly chlorine. But this has not been the case. I've had to add acid every week because my pH and TA don't change after I add chlorine and acid. I thought that adding liquid chlorine did not affect pH long term but this doesn't seem to be the case for me. Is this right? Do I need to add acid every time I add liquid chlorine to counteract the pH increase of chlorine?

I am using the pool calculator to know the amount of acid and chlorine to add. I usually add liquid chlorine first, wait 20-30 min, and add the acid. I add them in front of a jet or sometimes around the perimeter of the pool.

Latest results:
FC: 5.5
CC: 0
pH: 7.8
TA: 125
CH: 725
CYA: 140
Temp: 80

Thanks,

 

[mknauss]

As your water evaporates, your fill water, which is high in TA, raises your TA. Your pH rises due to aeration (waterfalls, wind, etc) with the elevated pH. You will add acid very regularly, I do it twice a week during high evaporation times.

I am puzzled that you feel adding liquid chlorine once per week is sufficient. Daily during the swim season is needed to keep your pool FC level above minimum.

Also, the FC you show above is far too low for the CYA your report. You need to exchange over half your pool volume to lower your CYA.

 

[jorgeL]

Thanks for the explanation! I just tested my incoming water and it is high in TA and pH. pH is ~7.7 and TA ~150. It makes sense why both of those numbers do go up over time. The one thing that does not make much sense is that my pH does not change when I add the chlorine and acid. I test the water at sundown, add the chlorine and pH after that, and then re-test the next morning. At re-test my pH has not changed to the expected value, it barely moves, if any.
I add chlorine and acid twice a week. I raise FC up to 9-10 and it goes down to 5 or so when I add more. I realize it is below the recommended number for my CYA. I'm thinking of converting to salt water.

 

[mknauss]

With your elevated TA, your pH rises back up very quickly. Test your FC and pH each day. Adjust as necessary with liquid chlorine and acid.