Difficulty measuring pH

[bennionr]

I noticed recently that when I measure the pH using the kit my pool builder gave me, I get different results than using the tf-pro. Using the pool builder's kit, which uses a chlorine neutralizer prior to the pH test solution, the pH looks pretty good. I'd say 7.7 or 7.8. Using the tf-pro, it looks more concerning, like 8.1 I think. It's hard to read though because the scale is so light. I just recently bought a refill for the tf-pro, so the chemicals are fresh. Leslie's seems to agree with the pool builder's kit, saying it's only 7.7 or so. Am I doing anything wrong in the testing?

Levels:
pH 7.7-8.1?
Chlorine: 16
TA: 80
Salt: 4200
Calcium: 775
CYA: 90
Borates: 40

Thank you!

 

[JohnT]

That comparator doesn’t seem right to me.

@Sarah and Nate

 

[TinFoilHat]

PH is not accurate over 10 ppm of chlorine. How did your chlorine get so high, assuming you tested it properly? The two comparators you have can't measure 16 ppm. You need to follow the TFPro instructions for using their kit for Chlorine testing. That would use the tall tube that says "Chlorine" on it. The comparator is basic and mostly for quick tests of low chlorine and normal PH.

 

[sande005]

I assume he did use the dpd version for the Cl. I agree that the Tftestkit comparator doesn't look right as far as its colors in the picture.

But, @TinFoilHat has an extremely valid point - pH readings are invalid when Cl is over 10. At least with the TFP test kit. No idea about what the pool store uses for chlorine neutralizer, or what effect using it may have on the pH reading.

 

[mknauss]

Neither sample has any purple hue to it. So in the mid 7's.

Adding sodium thiosulfate to a pH test sample changes the pH.

 

[bennionr]

Yes, I did the dpd test for the chlorine measurement. I haven't used the comparator for chlorine measurement.

I've been keeping the chlorine that high because I was going for 15% of CYA, which I thought was correct. I have my SWG set to 20%, which keeps it that high. Now I'm realizing that's probably too high so I'll turn it down.

I agree the comparator doesn't look right. I think water has been leaking inside and diluted the colors. I'll order a new one.

Thank you everyone for your help!

 

[sande005]

From the tftestkits.net site, here is what the colors on the one they ship should look like:


They sell one from Taylor also, with black caps, that has the same range. In the product photo they used, the Taylor colors are more vibrant. But who knows if that is the case in real life, side by side.

Finally, if one wants to dig around on the Taylor site, as well as Amazon, there is a Taylor comparator that has finer gradations. 0.2 steps, instead of .3/.4, although the range is only 7.0-8.0. Uses a different reagent, though.

 

[ajw22]

From the tftestkits.net site, here is what the colors on the one they ship should look like:
View attachment 630303

They sell one from Taylor also, with black caps, that has the same range. In the product photo they used, the Taylor colors are more vibrant. But who knows if that is the case in real life, side by side.

Finally, if one wants to dig around on the Taylor site, as well as Amazon, there is a Taylor comparator that has finer gradations. 0.2 steps, instead of .3/.4, although the range is only 7.0-8.0. Uses a different reagent, though.

Note that picture on the TFT site has the colored caps reversed. I emailed @Sarah and Nate at their TFT email about it.

 

[Sarah and Nate]

I noticed recently that when I measure the pH using the kit my pool builder gave me, I get different results than using the tf-pro. Using the pool builder's kit, which uses a chlorine neutralizer prior to the pH test solution, the pH looks pretty good. I'd say 7.7 or 7.8. Using the tf-pro, it looks more concerning, like 8.1 I think. It's hard to read though because the scale is so light. I just recently bought a refill for the tf-pro, so the chemicals are fresh. Leslie's seems to agree with the pool builder's kit, saying it's only 7.7 or so. Am I doing anything wrong in the testing?

Levels:
pH 7.7-8.1?
Chlorine: 16
TA: 80
Salt: 4200
Calcium: 775
CYA: 90
Borates: 40

Thank you!

View attachment 630228View attachment 630229

Hi there, something is definitely defective with that comparator and I’d love to send you a new one free of charge (or refund you if you already purchased a new one). Looks like the colors are washed out for sure. Email me your order details and I’ll follow up.
Nate