PH drop

[FloridaPoolNewbie]

What would cause a PH drop from 8.0 down to 7.1 overnight? Tested yesterday afternoon and while we did get some rain last night, it wasn't a ton. All other values below. I'd like to raise it a bit today as we're having some folks over to swim. My tap water is 8.0ish. Should I replace some water volume or is there another value I can raise that would quickly raise the PH. Maybe point the jets up to the surface for a while?

FC- 9
PH- 7.1
TA- 80
CH- 275
CYA- 70
Salt- 3600
Temp- 87

 

[ajw22]

How do you measure a pH of 7.1?

 

[FloridaPoolNewbie]

How do you measure a pH of 7.1?

A digital PH meter. Also verified on the standard drip test and it's hovering around 7 based on the color.

 

[mknauss]

With a TA of 80, the pH will not be at 7.1 for long.
The only thing that lowers pH Is adding acid or acid products. If you added neither, I would check your pH with a drop based test.

 

[duraleigh]

Agree with all above. Even if you don't discover the problem, leave your pH alone and let it rise naturally.

 

[JamesW]

What would cause a PH drop from 8.0 down to 7.1 overnight?

Probably test error.

 

[mgtfp]

I remember a thread a while ago, where a "helper" added muriatic acid instead of liquid chlorine to the pool. Any chance something like that might have happened!