Just got my pH tester...and

[hilljack13]

I came out to 7.96 pH on my "filtered" tap from the fridge. I had some distilled water and it tested 6.8. I need to recalibrate since it was the first time I used it. Do the numbers seem off? I figured the distilled would be dialed closer to 7.

 

[MaxStout]

Meters don't accurately measure the pH of pure water--not enough ions for it to get a reliable reading. Use the calibration solutions.

 

[day_trippr]

All water will pick up CO2 with a resulting drop in pH, and very low TDS water like distilled or good quality RO can easily turn acidic given enough time and the typical LDPE plastic containers that allow CO2 to pass through. If you wait long enough you can get distilled water to register in the 5.something range.

Yes, some meters have increasingly difficult time reading accurately as TDS approaches zero so I wouldn't use the numbers literally but they still make the point that distilled water containers rarely register as 7.0 pH for long if ever...

Cheers!

 

[VikeMan]

You'll never be able to calibrate your meter using water, distilled or otherwise. Calibration solutions are the only way.

 

[mabrungard]

The pH of any water sample is meaningless and it can't be used to infer calibration. As VikeMan stated; you have to use calibration solutions to assure your meter is reading correctly.