High acid demand

[meatloaf]

I had this problem last year and I have it again this year. I have to add 14 oz per day of 29% MA to maintain a PH of 7.5. I usually test at 7:30 AM. The PH reading is 8, I then add 14 oz of acid and 1 hour later I test again and the PH is 7.5. The next morning it's back to 8. The only answer I have for this is that it has been windy. Could the dust blown dirt cause the PH to rise that much?
I drained the pool over the winter and acid washed it so I'm starting the season with fresh water.
Test results are:
FC 3 (I add about 24oz per day after the sun goes down)
PH 7.5 - 8
CYA 40 (I used pucks at first to raise the cya, now I use 10% liquid)
CH 330
TA 60
Temp 80*
Pool Volume 10500 gallons
Sand Filter

Thanks

 

[Suziqzer]

Do you have a water feature running? Those aerate the water and can cause ph to rise.

 

[meatloaf]

No, none running at all.

 

[crookm11]

By any chance is the pump sucking in any air and spitting the air out the returns? Could the floor jets be doing the same thing?

 

[meatloaf]

There's no air being sucked in (no bubbles in return) and the floor jets have been disconnected and sealed, I had broken pipes under the pool.

 

[duraleigh]

You probably replace a lot of water out there in AZ. That surely wouldn't account for all of it but what is the pH of your fill water? It might be a contributor.

 

[meatloaf]

Fill water PH is 7.7

 

[flintstone]

Anything that creates water turbidity will lead to increases in pH. I don't think wind and rain get their share of blame for the problem because they are intermittent in most locales. I get lots of wind and have constantly rising pH, except in the deep part of winter. Wind definitely raises pH. Your sheer descent will contribute to the rise, as well. It's OK to use muriatic acid in consistent doses as long as you monitor it well and don't overshoot your target.