How often do you calibrate your PH meter?

[Hackerman]

I like this new HM Digital meter. With the 2 of them, I was able to stabilize the Milwaukee but I still like the HM much better. Faster readings, auto off (big one for me LOL).

Strange thing today... I measured all my water. Started with calibrating solution...7.0. Then, the Deer Park... 7.2. All OK. But then I measured my tap water. One was fresh out of the tap and had a strong chlorine smell (as always). The other had been sitting in a 1 gallon jug for a couple days (as I always do).

The water that had been sitting measured 8.0 but the water straight out of the tap was 7.2.

I am new to PH but isn't that odd that it would have a higher PH after sitting?

I am going to grab some PH down today and play a little.

 

[DrFever]

Hanna owner here recalibrate weekly My water from tap comes out @ 7.6 so if and when i use my ph meter first thing i do is tap it if she reads 7.5 - 7.6 i leave her alone
just invest in some calibration fluid also PH up and ph down i find as i add nutrients my PH drops even tho most Cem nutrients have some sort of PH buffer in them chances of ph dropping will be likely

 

[skullcandy]

every 2-3 weeks when in use