Distilled water pH test


Hi everyone, I started hydroponic system and I went with distilled water ( I add calcium and magnesium later). My problem is when I go to test pH it give me a very different reading than the drops, I use Apera PC60 5 in 1, bought for around 150€. Today I read on there site that the item is specifically not for distilled water so I returned it, do you know which pH digital tester I should buy at approximately that price range? So far looking good but relying on drops and I want a precise reading.


As far as I know, they are all unreliable with distilled water due to the nature of the mechanism by which the readings are taken. To me I would rely on calibration as my benchmark. That’s why they have ph 7.0 Reference Solution.


There are digital meters specifically for distilled water but they cost around 500€, so was hoping someone came up with an easier solution.


Yeah, I should have said within the price range. Why so precise?


What do you mean? I want the pH to be as close as possible to 5.8


@Myfriendis410 is correct, you can’t realy pH distilled, demineralized, or otherwise “pure” or zero ec/ppm water. Or maybe I should say you don’t need to, this level of pH accuracy is not needed for home hydroponics.

The pH scale stands for “potential hydrogen” and is a scale of acidity and alkalinity, with 7.0 being neutral and above 7 is alkali or “basic”, and below 7 is acidic.

If water doesn’t have any dissolved minerals for hydrogen ions and anions to create acids or basic compounds, like purified water is lacking, then it is generally going to be neutral in pH, or pH 7.0 and so you don’t really need to measure the pH of the water until after you mix your nutrients and let it stabilize.

Demineralized or purified water can show a acidic reading from absorbing CO2 from the atmosphere, but this is a very weak acid, and it will not really “hold” or alter the pH of anything it is added to as it is such a weak acid when formed from regular exposure to air in this way. And again the reason you don’t really need to measure the pH of this very pure water.

Add your calcium and magnesium, mix very well, and the let sit for a little bit, maybe 10-15 minutes, for everything to stabilize, then test pH, adjust pH and mix and let stabilize, and repeat, until you reach your desired pH, 5.8 for hydro and 6.5 for soil.

Happy growing,



Yes, but think about this for a minute. @Laqwanies

Hydro has been done successfully for decades. When the state of the art was a test strip. Many growers rely quite successfully on $10 and $20 digital meters which after all will not ever need to be accurate in distilled water but in a mineral solution at 5.8 ph. For one to achieve functional accuracy any number of inexpensive devices, IF FREQUENTLY CALIBRATED, will keep you in the sweet spot.


So when I add the nutes and calcium and magnesium the pH will show “normal” results?


Actually you’re right about that, thanks man


I know, there’s a lot of stuff to this! And I thought it was a weed hahaha!


Yes, after you mix some minerals into your water, and let it stabilize, you should be able to get a “true” reading of your pH.

Whenever you add more minerals or nutrients to your water, it can have the potential to change your pH.



Do you have any idea which digital meter I should get which does a decent job?


Great ! Thankyou


What you have I am sure is more than adequate for your needs.

In fact I just purchased a Apera AI209 PH20 for testing pH and I am very impressed with it for the price.




I just bought the Apera PH20. It is a bit more than the $10 pens ($48 I think) but less than the next one up with a replaceable tip. That one is around $100. It seems to be a good unit and has a 2 point calibration in a nice kit.


I bought the Apera PC60, so that should be fine right guys? Both of you bought the same pH nice.


yes, I think you’ll be very happy with the PC60


PC60 5 in 1 I’ve got, I just hope it’s worth the expense.


I just bought the Apera ph 20 also. There were at least five recommendations in my thread for this meter. I broke the last two meters I had and they assured me this one was tougher. Seems to be a very high quality meter.