High Ph, discrepancy between Taylor kit and strips

[Btabor73]

Hello all. My Ph is constantly high - above 8.2. Every week, I'm adding nearly a gallon of muriatic acid but when I test it again the next week, it's off that chart using the Taylor kit. The Taylor kit is brand new to replace one with expired chemicals. When I test the pool with some test strips, Ph is right in the perfect range. I know everyone says trust the test kit chemicals more than strips, but the test results for all other elements (Chlorine, CYA, hardness, alkalinity) are all very similar between the Taylor kit and the strips - only the Ph is the big outlier. I tested my tap water using both the Taylor kit and the strips. The strips and the Taylor kit were very close in this case for all the elements. Why would I get similar results between the Taylor kit and the strips testing my tap water, but such Ph extremes with the pool water?

I have a salt water pool, 21,500 gallons, pebble sheen plaster, about 8 months old. Thank you for any advice you can provide.

 

[Flying Tivo]

You need to reset your ecu. We call them guess strip. Just test with the Taylor and believe innit

 

[mgtfp]

Welcome to the forum, great to have you on board.

Best would be if you could post a full set of your water parameters.

What is your FC? One thing to keep in mind is that above 10ppm, the pH test starts showing false high.

Did you test pH straight away after adding acid? (Edit: With straight away, I mean about half an hour later, with the pump running to let the acid mix in).

And what is your TA? With high TA it wouldn't be surprising for pH to climb back up quickly.

 

[Btabor73]

You need to reset your ecu. We call them guess strip. Just test with the Taylor and believe innit

What is ecu?

 

[Btabor73]

Chlorine is 4, TA is 110, free chlorine is zero. I didn't test ph immediately. I waited a week.

 

[mknauss]

How do you have a 'chlorine' of 4 and free chlorine of zero? Just report test results from a proper test kit.

What Taylor kit are you using?

 

[Btabor73]

I'm using Taylor k-2006c with FAS-PD. Sorry wrong terms. Free chlorine is 4, combined chlorine is 0

 

[mgtfp]

Chlorine is 4, TA is 110, free chlorine is zero. I didn't test ph immediately. I waited a week.

I suspect you mean FC is 4ppm and CC is 0ppm? (Edit: you were faster....)

With TA 110 and sufficient aeration pH can rise back up pretty quickly. And with a starting pH in the dark red you actually don't know if you started at 8.2 or maybe even 8.4.

You should test pH about half an hour after adding acid with the pump running to confirm that pH got down to the expected pH.

Are you adding Alkalinity Increaser?