Noticed something interesting with PH testing - Taylor 2006

[dykes26]

My first test always comes out low- Around 7.2-7.4. I dump it out and refill and this test seems to be accurate. I have run several tests at the same time and only the first comes out low. Am I safe to assume that the second test is more reliable than the first. Thanks in advance for your response.

 

[gordiec]

Guess I'll have to try a couple back-to-back pH test tomorrow and see what happens.

Do you rinse your vial out with pool water before doing the first test?

 

[dykes26]

Yep!

 

[Richard320]

When you say you refill it, do you mean you go scoop more water out of the pool for each test, or do you have a container full of water and you just pour some more of the same sample into the test block?

I have noticed that when I get a reading, I set the block aside to do the other tests, and when I look at it again in a few minutes, pH has gone up by about .2
I have been assuming it's outgassing CO2, which is also why I just invert the test block once to mix - no more shaking it. That's also why pH is the very first test I run.

 

[dykes26]

Refill is a dumping of the old water, flushing it with the pool water and then adding fresh h20 from the pool.

 

[No P in my ool]

If you do your chlorine test first with the lid on rinse the lid before you do the PH test.

 

[gordiec]

Sorry, got home late yesterday so I didn't test the pool until this morning. I did back-to-back pH tests using the Taylor K-2006 kit, both came in at 7.6. I don't know why you get two different readings.

 

[PaulR]

Do you also test chlorine using the yellow OTO test at the same time? I found that staring at the OTO test will cause some color fatigue. For example if I look at the pH, then at the OTO, then back at the pH--the pH looks like it has gone up, because my eye isn't registering the yellow as strongly. An orange-ish pH result will look distinctly redder the second time.
--paulr

 

[dykes26]

super! Thanks for your reply. I did some experimenting as well and PH needs to be tested first for a correct first read result. If you check Chlorine first you get a lower ph reading the first time out and a accurate reading the second time through.