Technical pH calibration

Hello, I bought a decent $30 pH meter for water testing. I calibrated it using the 3 pH solutions enclosed. No problems so far.

My tap water tested 8.03 pH . So I adjusted my last watering to 6.5 no problems again.

But then I pulled a new sample from the tap this morning and took it into work to test on our $2000 pH tester. It tested at 7.53.

So here is my technical question: I know pH changes the more you let the water set out to where dissolved CO2 for example volatalizes out into the air etc and this can change the pH.

So, should I err on the side of caution and shoot for a slightly higher ph with my home cheap pH meter?

Thoughts or suggestions???

I would check the same water with both ph meters to see how accurate your cheap one is…


How do you err on the side of caution when you question your pH measurement?

That drove me nuts so I use pH indicator drops in test tubes. I imagine it is worse knowing about the good equipment like you have at work.

Not really helpful😁unless it is.

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Maybe I’ll just steal the one from work? On second thought…

I mean the pH scale is logarithmic so anything like 0.5 from neutral 7 is not really that far off… but jeez it’s not as exact as I’d like it to be.

This, exactly. I test my tap water all the time just to have a good baseline. It fluctuates between 7.6 and 8.1 depending on the day - I assumed it had to do with the municipal water supply’s filtration system.


Mine changes. Not sure what as I haven’t checked straight tap water in a long time.

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