Determining if a pH probe needs to be replaced
 

I've got a Apex setup with a pH probe and just wondering how to tell when a pH probe needs to be replaced?

What are the signs?

Is it normal for the pH to change throughout the day?

What is an acceptable range?

Thank you!

I had my pH fluctuate from 7.8 to 8.4 sometimes throughout a day. If you're really concerned, get some calibration fluid and re-calibrate.

Warren,

Thanks for the quick response! :biggrin:

I just replaced my pH probe and calibrated on Tuesday. The pH peaked at 8.43 with a low of 8.33.

Would you know what the typical pH swing should be?

I just set TEMP COMP = ON for my Apex. Perhaps this will provide me with a more stable reading.

When I talked with a Neptune rep, he told me a regular ph probe should be replaced every year, a bit longer with a lab grade one.
I been using the same probe for 3+ year and only had to recalibrate a couple of time


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Usually a good sign of a probe that is low quality or needs replacing is how fast it reacts to pH changes. If you stick it in a calibration fluid and it takes forever to stabilize it's probably past it's best before date. Although that doesn't necessarily mean it is inaccurate once calibrated.