pH meter calibration help

Was trying to mix up some cal mag and distilled water this evening and my pH meter is either not working correctly or I’m just stupid…maybe both. Put some pH down and it went way down, some pH up and back way up…put a few drops of down in and it went up…put more and it stayed the same…put more and it stayed the same. You get the picture. So I thought recalibrate but I don’t have the 6.86 solution. I have some pH up tho…would that work and cause it to be .14 off? I have the 4 or pH down and I have the 9, just not the 6.86. Any ideas other than buy some more crap (this just isn’t possible at the moment)? Is there a special way to make the pH up and down cooperate lol. And yes I’m mixing it before testing. I’m stirring and shaking. I’m at a loss at the moment.

PH meters suck. I have a decent one and that’s the only way I get by. I had an Amazon one and it didn’t work right even once.

If you’re only .14 off with a PH meter, that’s a win in my book.

I wish I could be of help.

My only suggestion is go to the manufacturer website find some troubleshooting info.


@NeoGroR i got a vivosun but I thought it was good but the readings just aren’t adding up and would explain why I had such trouble with nutes before as well. I’m a fairly bright guy (usually) but just wasn’t sure if there was some mix or what not I could use to get the 6.86 solution. I may have to bite the bullet and order some of the powder. Just annoyed the meter may or may not work lol.

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The powder is the worst!

Go to your local hydroponic store. They’ll help you out. My local shop tried to calibrate mine for me. Told me I ruined it.

Did you know you should store your meter soaking in a solution? Yeah, neither did I until I visited the hydro store.

I bought an Apera … saved my grow, I was watering with 5.0 and had no idea


Soaking in a solution?!? What kinda sorcery us this lol


There is calibration liquid, much better than the powder.

I calibrate mine once a month just for peace of mind

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Ph is so dang important, why mess around.

Or… you could just use the “Ph Perfect” line Of nutrients and never have to worry… but that seems like sorcery I want nothing to do with until I know someone who’s done it.

Do you have a TDS meter? You didn’t mention how much calmag you added to the distilled water. If your ppm is low you’re not going to get a legit reading from the ph meter. Also if the ppm is low, adding ph up or down is going to drastically change the PH.

And yes, the crystal ph buffer sucks. You can toss the 9, it’s not needed for the ranges you’re looking for. If just save up $40 and grab an apera ph20. It comes with calibration solution so no more mixing that crystal crap and it holds calibration for much longer periods. I calibrate mine once a month and could probably go a couple months cause the worst it’s been off is by 0.1.


@BobbyDigital yes I do have a TDS meter and I did not check the ppm of either gallon and finally just used plain distilled water but I’m fairly sure my ladies need that cal mag at least. I added 5ml to a gallon of water.

What I’m saying is distilled water (0ppm) plus your calmag may not have been enough ppm to give you an accurate ph reading. 5ml should have put you at around 150ppm, which is enough to get a good reading, but without checking the ppm you won’t know for sure. And if you’re using GH ph down, it only takes one drop to make a difference at that ppm level.

This will cover most ph meters for a long long time. Unless you really screw up. Ya, don’t ask!


@BobbyDigital I used the meter a few days ago to test a few different water sources and even distilled, purified and natural spring water all read between 7.6 and 8.0, TDS was 0 for all but spring water. I’ve had a real struggle trying to get nutes handled and a bum pH meter would make a lot of sense.

Calibration depends on the pen and the number of calibration points it requires. Some pens use a 3 point calibration others 2 points. Calibrate following the mfg directions. Distilled and RO are blank canvases. They have no dissolved solids in them so it is impossible to take either PH or PPM / TDS readings before adding something. I collect and use rain water and have the same problem.
Start with 1 gallon of distilled water.
To it add your desired concentration of CalMag
Take a PPM / TDS reading, if over 100 should be able to get reliable PH reading.
Take PH.
Add your PH adjuster ± in VERY small amounts. I use a 1 ml dropper. Mix, let stand and take PH again. Repeat as necessary.
Some would argue PHing distilled water with CalMag is unnecessary.


You can’t test these waters for PH. They are literally neutral. There is no power of hydrogen (Ph) in them. Any reading you get from these waters is the meter just throwing out a number because it doesn’t want to disappoint you.


@beardless and what would you say to those who say distilled and cal mag is fine without pH’ing the water? I was under the impression the plants only took in cal mag at a very specific range like 6.5 to 6.7 or some such? I don’t think the girls are in any danger at the moment but I’m noticing some changes like tips lightening and I’ve seen some purple stems although they are still pliable so not sure if that’s mag deficiency or just a generic thing. Can’t really see the purple on the stems in the pics but it’s noticable.

I believe the reasoning is the distilled water with calmag will take on the PH of the medium it is applied to.
My plant ailment skills suck. You definitely have a deficiency. Yellowing leaves with green inter veining with tip curl. Search with these descriptions because that is what I would have to do. I won’t even venture a guess

@beardless to be fair the most purple is on the plant in the pic, which is my runt and has had many issues over it’s rough life lol. For instance it’s looked droopy since it’s first set of leaves and sporadic stretching/growth. I don’t doubt it’s in bad shape, I’m just saying I’m not sure it’s ever been in good shape lmao. The other girls look a bit better and “normal”

Edit: the yellowing on this lady is just the flash. She’s a looker in person :joy:

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The calibration of your meter is no better than the solution that you use to calibrate it with. ph up and down is not a buffer solution. When doing a 2 point calibration always start with your 7 buffer solution first. Also when calibrating the meter be careful not to contaminate your Solutions . Clean between going back and forth between the two buffer solutions to check 7 pH an 4ph . As mentioned a quality pH meter much easier to work with.

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As far as I know purple leaf stems is not an issue. My current grow of northern lights have them. My Amnesia haze also had it. Sometimes it is attributed to magnesium deficiency but if you are doing calmag that should take care of it. Another reason is genetics. I believe it occurs more frequently with strains having haze genetics in it.

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@kellydans hmmmm on the vivosun meter it says you need 3 to calibrate. Or rather it says to do them one after the other etc. The bottle of pH down says it’s a solution for calibration but it may be a solution the way Walmart cola is the “same” as regular coca cola lol.