Ph pen issues inconsistent readings

I’m having an issue with this pen

It’s dead on when I’m checking the ph of my water when I’ve added nutes.
But when I try an ph plain water I get readings all over the place. I’ve calibrated many times but I still can’t figure out why it goes wacky with just plain water. Any thoughts ?

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I’m not familiar with that model but it may have a replaceable probe that’s usually what goes bad on ph probes. You may or may not be able to get one. Good luck

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What kind/type of water are you starting with ?
Distilled water and RO (if taken low enough) won’t read correctly due to low EC (electrolytic conductivity) amounts…not enough to conduct properly to get proper reading.
When you add nutes or anything really it changes the EC and then you get a reading.
Not a pro by any means on growing or water, but thats what I have read in a few comments.


I agree with wicked ale the best way to get a reading on ph or conductivity is gently stir probe in container don’t let probe touch sides or bottom of container.

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Plain tap water but it has low Ppm of 48ish

I’m not sure of how low it needs to be before its too low, but mine starts around 120 ppm and I get pH reading of 7.
I’d say your fine as long as your putting the correct pH’d fluids into the plant…just a guess tho…lol

@WickedAle, yes, you are exactly correct…was just trying to make it simple and not scare anyone with big science stuff :man_scientist:

@WickedAle @kellydans @T0Y
Would it be damaging if I added the water without getting the ph right on? I’m growing in coco if that makes a difference

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With what I’ve read it doesn’t seem to matter what the water values are when you start for the most part…could be 0 to 1000 ppm and ph of 5 to 10 (random values not really real…lol)
As long as you fix everything to the plants desired amounts of say 5.8 pH and 500 ppm it should be fine to use…not sure of values for coco or your grow needs…I do hydro.
Maybe follow a coulpe coco grow journals and see what they used that worked and you can also see what may not work too…journals are great for that…lol

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They have you set. For better understanding, check out what “potential hydrogen” is beyond measuring base/acid.