Testing PH levels

Daniel76120

New member
Oct 7, 2020
2
Fort Worth
Pool Size
9316
Surface
Plaster
Chlorine
Liquid Chlorine
Hello there,

I have a Taylor test kit 2006-c, and I have a question about PH testing. So this morning I did my initial testing and my PH was at 7.8-8.0ish, and I added 4 drops of the acid regent to drop it to 7.4 ish and added my acid dosage to my pool. I ran my pump for 2 hours and re-tested. When I re-tested and inverted the test tube I initially got 7.4, after a few seconds (like 10 seconds) I noticed that it kept raising. I got back to 7.8-8.0. Is this normal? Should I trust my initial re-test or am I suppose to let it sit for a few seconds? I am kind of confused on what to do.

My pool is less than a year old, so it tends to have high PH.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
25,667
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Welcome to TFP.

Stay with your first reading of drop tests.

Test colors will change if you let them sit after the test. Ignore that.
 

mgtfp

Bronze Supporter
Mar 5, 2020
975
Melbourne, Australia
Pool Size
66000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Astral VX 7T
What is your FC?

High FC turns the pH-indicator into a different type of indicator that changes to red already at lower pH, which makes you think that pH is high, even when it's not.

The Taylor pH-reagent has additives that make it work up to about 10ppm FC. If significantly above 10ppm, the indicator turns red pretty much instantly. If only a little above 10ppm, it initially shows the correct colour, but starts to change to red after a few seconds - sounds like that's what's happening in your case.
 

Daniel76120

New member
Oct 7, 2020
2
Fort Worth
Pool Size
9316
Surface
Plaster
Chlorine
Liquid Chlorine
What is your FC?

High FC turns the pH-indicator into a different type of indicator that changes to red already at lower pH, which makes you think that pH is high, even when it's not.

The Taylor pH-reagent has additives that make it work up to about 10ppm FC. If significantly above 10ppm, the indicator turns red pretty much instantly. If only a little above 10ppm, it initially shows the correct colour, but starts to change to red after a few seconds - sounds like that's what's happening in your case.
FC was at 7 when I checked my PH, and that’s usually where it is at due to my CYA. One of my co-workers had the same problem and suggested I add one or two drops of R-0871 titrating chlorine reagent and that would help to give me a more accurate PH reading. I’ve done it twice so far and seems to work just fine.
 

mgtfp

Bronze Supporter
Mar 5, 2020
975
Melbourne, Australia
Pool Size
66000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Astral VX 7T
At FC 7, the Taylor test should work fine. I would not recommend to add anything prior to pH testing.

Other pH tests (not Taylor) start showing wrong results already at about FC 5, they don't have Taylor's additives that are designed to be pH-neutral.

Some test kits (like Blue Devil) recommend to add a drop of Thiosulfate chlorine reducer, but that has also an effect on pH.

Just use Taylor reagent and make sure it's not expired and properly stored (don't leave it outside in the sun, should stored inside), and you should be fine.