Will pH Read High with High FC And High CYA

[Michael1]

I was surprised that my pH seem to rise dramatically over a couple weeks, after raising the chlorine due to high CYA. I was also trying to get rid of some algae. At the same time, I got the pool pump system working better with better flow, so the spillway for the spa started working. Now I am not sure if I am reading high pH due to higher FC, or it is due to more aeration from the spa spillway. Will you get a different reading for pH with a pool with high FC and low CYA, and a pool with high FC and high CYA. I am not sure if I should be adding acid or not.

FC 25
CC 0
CH 750
TA 190
CYA 120
pH 8.2

 

[Wildcat]

Aeration will raise PH
High FC leads to false high PH readings

From what others have said, complete your SLAM, reduce FC to 10 or below and then adjust your PH

What was PH before the SLAM?

 

[pooldv]

Correct. PH test is not valid when FC is over 10. Finish the slam and retest PH after FC is under 10. CYA does not affect PH.

 

[Michael1]

Aeration will raise PH
High FC leads to false high PH readings

From what others have said, complete your SLAM, reduce FC to 10 or below and then adjust your PH

What was PH before the SLAM?

pH was 7.8 before SLAM.

Can an accurate reading be had if a chlorine neutralizer was used during the pH test?

 

[epro05]

No, that won't work.

 

[Richard320]

No, that won't work.

To expand:
Accurate pH test during shock levels with R-007?

 

[epro05]

Thanks Richard, I just spent the last 10 minutes looking for the very post you linked. I had those pictures in mind which I said "No, that won't work", but felt I needed to back it up with some evidence.

 

[Michael1]

Great information, guys! It looks like it is another reason why it is hard to operate a pool with a high CYA. You need higher FC even without a SLAM, but then the pH reading becomes distorted.

I'm learning so much here. Thank you very much!