pH normal fluctuations?

[BSBrewer83]

I received a ward labs water report nearly a year ago and my pH was 7.9. When im testing my water right im getting 6.75. I just calibrated my pH meter. Can pH have this great of change in tap water or am i doing something wrong?

 

[BSBrewer83]

Actually it is currently 6.85

 

[ajdelange]

Let a tumblerfull stand over night and check it again.

 

[BSBrewer83]

Ok 7.64 today. Thats a reasonable difference given the source of water is a lake in colorado.