Ph meters and distilled water?


Hey guys I’ve been having trouble out of my el-cheapo ph meter from amazon. I have been looking for a reliable one since ph has caused me problems before. As I was reading I came across an article saying that ph electrodes will not give accurate ph values of distilled or deionized water. All I use for my plants is distilled water since I don’t have a RO system. Is this true as I can only find this one article saying this? I don’t know what to do any suggestions?


This is true, but I can tell you from experience, I run distilled water in dwc with absolutely no problems and in Hydro you have to stay diligent about your pH.

I never have any problems using distilled


This is true, but the moment you add any solids (nutes) your meter will read correctly. It’s the lack of conductive material suspended in the water that prevents an accurate reading. Just add nutes and ph as normal.


What about seedling stage and veg? Since I’m growing autos with ffof soil @Myfriendis410 I wouldn’t have to add nutes till flower.


Can you link your ph meter to me? @TDubWilly


The Apera PH meter I use is a bomb proof dream. As a hydro grower it’s probably the single most important tool in my arsenal of tools, and well worth the extra dollars.


The only thing is; Is that some distilled water is around pH 8 However; Now that you mention it…How do we know that. Interesting. I am going to discuss this with the panelist on the podcast Thursday night.


What I use

I also have several Milwaukee pens. Most are posted in our Offical Buyers Guide at the bottom of the forum.

Blue Lab is a great company and offer this PH pen

hope this helps, lw



You might not want mine, its a little expensive

PH400 Portable pH Meter Kit, 0.01 pH Accuracy, 0-14.00 pH Measuring Range, 3ft Probe, 3-Point Auto Calibration, pre-mixed buffers included


Yea, I was looking at the apera ph20 but I saw where it stated it would not read distilled water so now I’m confused on what ph meter to buy since I use distilled water all the time. @Bogleg


Can you give me your advice on what you would do in my situation? I’m growing autos in ffof and don’t start using nutrients till preflower and only used distilled water with that being said how do I know I’m getting an accurate read of my ph in veg? Would me buying an apera ph20 better my situation now that I’m aware of not getting a completely accurate ph with distilled water? Because I don’t wanna buy a nice meter if I’m still gonna have to worry about my ph being off because of distilled water. (Which I use so I will have the lowest possible ppm without an RO system) @latewood


I believe every grower needs a PH pen regardless. Once you do add
nutrients to the distilled water you will get an accurate reading, and I
never had any issue getting accurate readings from my RODI water, so I am
not sure when someone says you won’t get proper readings.

I cannot make you buy a meter. That is something you as an individual has
to decide for you.

Happy growing :slight_smile: lw


I’m afraid you misunderstood my question. What I mean is what do you recommend I do if I don’t use nutrients till flower since I’m growing autos in fox farms ocean Forrest? If I don’t use nutrients till flower how do I know I’ll an get accurate ph read during veg? @latewood
Thanks :v:t2:


If you don’t want to add any nutrients in your soil at all then wash some of the nutrients out of your soil and out of the bottom of the pot, this water should have fertilizer in it from your soil. Take your run off water, add it to your distilled, then adjust pH…

Of course, it would be easier to just add the most minute amount of nutrients to your distilled water, it won’t take much at all, something as little as 10ppm or less should give you correct pH readings.



I was going to suggest adding something benign like a small amount of tap water to the distilled. All you need are some solids in suspension for the probes to measure current flow. This is why this type of ph meter is not appropriate for distilled water only. In your case with MJ, distilled water is actually not a very good idea as you will end up with deficiencies galore IMO. I would add about 10% tap water, or a teaspoon of Epsom Salts before any reading.


I’ve used this pen for just over a year now and works great. You have to clean and calibrate once a month according to directions which keeps it accurate. A small check mark will disappear on the screen when it’s time to service.


Very nice meter :+1::+1:

I have both the Bluelab and Extech meters and find them both to be excellent devices.

Any electrical/electronic measure of pH is an approximation. The only way that I know of to get truly accurate pH values is through titration (think back to highschool or college chemistry). That said, the approximation produced by quality meters is very close and certainly good enough for horticultural purposes.


Even better


Yea decided to start using tap water since it’s ppm is only 151 out the faucet. @Myfriendis410


I’ve been growing with my city water which is around 500 ppm. I just added R/O water capability to my grow space. 150 ppm is wonderful!