Why would pH keep dropping?

[negativez0]

My TA, CYA, and CC have been rock solid since I started this method. But my pH keeps falling. I point the return up and aerate the water for 2-3 days, which bring the pH up to about 7.3. Then in about 4-6 days it drops back down to 7.0.

What could cause this? Is there something I need to change to keep the pH from falling? I've only been aerating as the TA is already at the top of the recommended range and it seems any other method of raising pH can also raise TA.



My current results are below. My logs are shared as well. Thanks!

 

[mknauss]

Is the pool covered?

 

[negativez0]

Is the pool covered?

Yes, always has a solar cover on it when we're not using it

 

[mknauss]

Trapping the CO2. Remove at least a portion of the cover during the day.

 

[negativez0]

Interesting. I'll give that a shot. Thanks!

 

[JamesW]

It should not drop unless something acidic is added.

Are you using tabs or adding CYA?

If the TA is not going down, the pH should not be going down.

Are you sure about the TA?

 

[negativez0]

It should not drop unless something acidic is added.

Are you using tabs or adding CYA?

If the TA is not going down, the pH should not be going down.

Are you sure about the TA?

The only thing I've been adding is liquid chlorine.
I'm positive on the TA. I've followed the directions in my test kit exactly the same every time.