RO vs Distilled water

I starting using distilled water that I pH'd to water my plants with and then I had someone at a grow store tell me that Distilled water is bad for plants. Is this true? Should I only use RO water? They are both pretty much zero parts ppm right?

I highly doubt it...Never had a problem with it. I've heard this before too, but gotten no scientific explanation for it...Nature naturally distills its water, no???

I've read a couple threads on this just recently, both seem to be ok, but the distilled is said to have no micros in it, so as long as you PH it (seems to usually be low), then as long as you add extra nutes to make up for what is missing, you should be ok.

RO & distiller water have an EC 0.0 therefore no buffering ability and when u add the (acidic) nutes they will literally fall thru the floor, down to PH4-5. You need to either add cal/mag or a bit of tap water as a foundation. I use RO and this is necessary.


Remember that water can be too soft as well as too hard !!

I use ro water and my ph dont get anywhewre near that low, infact its bang on 5.8 most of the time. As for the cal/mag that depends on your base nutes, some have all the cal/mag you need others less so. I dont add it. Pointless mixing tap water with RO kinda defeats the objective.

Current grow RO and base nutes 4 wks in, healthy as can be.


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jimmygreenfingers said:

I use ro water and my ph dont get anywhewre near that low, infact its bang on 5.8 most of the time. As for the cal/mag that depends on your base nutes, some have all the cal/mag you need others less so. I dont add it. Pointless mixing tap water with RO kinda defeats the objective.

Current grow RO and base nutes 4 wks in, healthy as can be.


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I think most nutes are designed for hard tap water which is higher in ca and some mg. If I need an EC of 2.0 then it would definitely fall very very low. I use ca/mg to EC 0.3 to base my water. However each company has different values and I use Canna and Hesi in soil. Plants look great btw!

I am using technaflora nutes which have a fair amount of cal and Mg in the mix.

Most RO water will range from 5-50ppm depending on the age of the filters and source water quality. RO water will not be 0 ppm unless it is then ran threw a DI filter to remove the last little remaining TDS. I us 10-20 ppm RO water on my plants and I only use the 0 ppm DI water for my reef tank. I like to leave a little something in the water for the plants.

hunter22375 said:

I starting using distilled water that I pH'd to water my plants with and then I had someone at a grow store tell me that Distilled water is bad for plants. Is this true? Should I only use RO water? They are both pretty much zero parts ppm right?

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The grow store guy is wrong IMO. Yes using RO water or Distilled water without using some sort of Cal/Mag/Iron supplement your going to have problems. I'm no Scientist but to me when using Distilled or RO water with Cal/Mag, you will know that your water, after adding your Cal/mag/Iron, will have the correct ratios of these base nutes. Of course If I could use my well water I would just to save money but it's not possible with my well water. Also, if you ever were to mix nutes or experiment, you will know exactly what is in your water so you could make the proper calculations. Using Distilled water and Cal/Mag I harvested over a Pound and a half off of 2 plants. Of course the rest of my set-up helped with that but I'm just saying, I have had absolutely no problems using Distilled and Cal/Mag.