PH varies

[Fishy1234]

My question is, I see a trend where my first ph test is often very low 7.0 range and obviously wrong. I recheck and usually get a reading that coincides with the very nice meter. Today I had to check ph 3 times before it was same as ph meter and surprised to see 8.2. Each measurement was higher than the last. Is this common? on going issues with PH measurement lead to the purchase of a PH meter. With that said, I generally use the Taylor kit for measurement but compare it to the PH meter when in doubt.
FC 8, PH 8.2, Alk 80. CH 400. CYA 50

 

[Texas Splash]

Many complain about CYA testing difficulties, but the pH is often more tricky for me. I have a meter, but have found that it can be finicky as well and need calibration, so I usually stick to the drop test. Some folks will try adding 4 drops which helps them to see the color hues better. I find outside light under a bit of covered shade with a light background works best for me. But I go with the initial result after adding the drops and gently shaking the viewer.

 

[ajw22]

How are you sampling your water?

Are you cleaning your test vials well in between tests and storage?

 

[kellyfair]

I use the drop test, four drops instead of 5, and hold it up to my kitchen window. I’m almost always exactly the same color as the 7.6 block, and I call it a day!

 

[Fishy1234]

Maybe that's the problem, I rarely clean the vial. Usually I do the chlorine test, then PH. I do rinse the vial with pool water after checking chlorine, then check PH. Not sure why I'm getting yellowish color on 1st attemp.

 

[mgtfp]

Are you using one of those double comparator blocks for pH and Chlorine (OTO or DPD)? And you do the chlorine test first, discard the chlorine sample and rinse the comparator block with pool water (inside the pool or by using pool water from a sample bottle?. Could it be that you contaminate the water sample for the pH test with the reagents of the Chlorine test? Try rinsing a couple of times and maybe take the final sample for the pH test a bit further away from the location where you rinsed the Chlorine vial.

 

[ajw22]

Rinse the vial well before and after use and do the pH test before the chlorine test. Dry the vial with a paper towel after rinsing before storage.

 

[Fishy1234]

Are you using one of those double comparator blocks for pH and Chlorine (OTO or DPD)? And you do the chlorine test first, discard the chlorine sample and rinse the comparator block with pool water (inside the pool or by using pool water from a sample bottle?. Could it be that you contaminate the water sample for the pH test with the reagents of the Chlorine test? Try rinsing a couple of times and maybe take the final sample for the pH test a bit further away from the location where you rinsed the Chlorine vial.

Yes I have Taylor k2006. One side is large and other side is small vial for checking CYA level. I use the sample bottle to rinse the vials.

 

[Fishy1234]

Rinse the vial well before and after use and do the pH test before the chlorine test. Dry the vial with a paper towel after rinsing before storage.

I'll try it that way tomorrow

 

[Fishy1234]

Cleaning with fresh water and wiping with paper towels after each use seems to be working.
Thanks