High PH, treated, back up 24 hours later

[NormG]

Yesterday my PH tested right at 8.0. I treated with muriatic acid and tested about 6 hours later. Second test was 7.5. Today it's back at 8.0 after 2 tests. No rain or change other than that. What would cause this?

 

[TinFoilHat]

What is your FC level? Above 10 ppm of CL will skew the PH reading. Did you recently acid wash or put new plaster in? That can use excess MA for a year or so. Also, what is your TA level? It can mess with PH as they equilibriate with each other.

 

[PoolStored]

High TA and low pH are the main causes of pH rise. My guess is that your fill water TA is high. Have you tested your fill water for pH, TA and CH?

PH TA Relationship - Further Reading

www.troublefreepool.com

 

[Bperry]

Yesterday my PH tested right at 8.0. I treated with muriatic acid and tested about 6 hours later. Second test was 7.5. Today it's back at 8.0 after 2 tests. No rain or change other than that. What would cause this?

TA higher than 60ppm.