RO water kills my plants.

Last December I installed a new reverse osmosis system and ran my hard tap water through it. Out of the tap it's ppm is around 640, and its pH is higher than the recommended for growing. This system managed to take the water down to 30 ppm and 6 pH. The problem comes when using it on my plants, lately I tried it in my cloner and it made them all shrivel up. So next time I took a batch of clones I used RO water from the store and had no problems with it. And when it comes to my bigger plants it's the same issue it makes my plants shrivel up and die.

So my question is what contaminate could possibly be entering the reservoir during it's filtration process that is causing all this duress.

recheck your ph. make sure you add cal-mag with your flowering plants when using RO.

I've checked my pH several times and added cal mag in all stages of the plants growth when I was on the RO.

Don't use r/o in a cloner. tap works much better, Also, are you p.h ing your water after adding nutes or before?

I never adjusted the pH in the RO because it seemed to be stuck at 6. I only adjust my tap water in which I use the pH first, but my tap water doesn't seem to hurt anything.

You got a point the tap water will kill any algae.. I always clone in tap water and bust beans in tap..

VICTORYGARDENSHYDRO said:

Don't use r/o in a cloner. tap works much better, Also, are you p.h ing your water after adding nutes or before?

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Truckn said:

I never adjusted the pH in the RO because it seemed to be stuck at 6. I only adjust my tap water in which I use the pH first, but my tap water doesn't seem to hurt anything.

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straight r/o has no buffers and a p.h test would be inaccurate because of that. you need something to act as a buffer in the r/o water then you can p.h it and adjust accordingly.

VICTORYGARDENSHYDRO said:

straight r/o has no buffers and a p.h test would be inaccurate because of that. you need something to act as a buffer in the r/o water then you can p.h it and adjust accordingly.

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When I was using the r/o water I was also using advance nutrients and that stuff is suppose to to have perfect pH. Whenever I tested it, I use the colored drops method which isn't the best it still came out a reasonable pH number.

Regardless of what additives were in the r/o water it would kill plants. Switching back to tap seemed to heel them and hasn't caused any harm since.

What kind of soil are you using? or soiless

here is my .02$. make ur r/o water and then add ur nutes and then check the waters ph. If ur r/o is putting ur water ph @ 6.0 and then u add nutes to it, the ph is gonna go down..like way down depending on what kind of brand u use. most nutes have ph buffers that will drop the ph to the 6.2-6.6 range without having to add any decreaser but ONLY IF THE PH LEVEL STARTS OUT HiGh!. if the ph is low to start with and u add nutes, the ph is gonna drop even more. the buffer in nutes will only LOWER ph..not raise it. the only reason im talking about only the ph is because if ur plants are shrivling up and dying as quick as u make it sound, i would put my money on a PH issue. R/O water= Low PH..Nutes= Low PH..put them together and u got super low PH

So you've only had this experience on one batch of clones and one run? You should try it again with your home system RO, since you successfully did it with a new variable (the store bought RO water). Did you forget to turn on the pump? lol. Also, do you run your pump 24 hours? What is the room/water temp? Are you cutting your clones underneath, or into water before placing in the cloner to prevent embolism? What rooting hormones and additives are you using? I guess I'm just going through everything I've ever experienced that has given me some type of problem, but I've never had them just shrivel up and die with a working pump, and pHed water, regardless if there was any rooting hormone or not.

Grown n Oregon said:

here is my .02$. make ur r/o water and then add ur nutes and then check the waters ph. If ur r/o is putting ur water ph @ 6.0 and then u add nutes to it, the ph is gonna go down..like way down depending on what kind of brand u use. most nutes have ph buffers that will drop the ph to the 6.2-6.6 range without having to add any decreaser but ONLY IF THE PH LEVEL STARTS OUT HiGh!. if the ph is low to start with and u add nutes, the ph is gonna drop even more. the buffer in nutes will only LOWER ph..not raise it. the only reason im talking about only the ph is because if ur plants are shrivling up and dying as quick as u make it sound, i would put my money on a PH issue. R/O water= Low PH..Nutes= Low PH..put them together and u got super low PH

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This is interesting, never once did I consider it being too low. But Advanced advertises that their nutrients are pH fixing, when I did tech support they assured me that it to be a nutrient build up and told me to flush.


The cloner was not the first occurrence of this just the most recent. I have some pictures and documentation of it killing my big veg plants in my rollitup post from a year ago I can dig em up if it helps.

The ultimate conclusion I came to was there was some very rare toxin or pathogen entering somehow through the filtration process. So I just don't use it.

Above post^^^ Exactly!

In any case the steps you take should always follow this.

Fill up your reservoir or watering can and nute it accordingly. Once the appropriate nutrient level has been reached you pH it to 6.0 or whatever you prefer (thats where i keep mine in my res). IF its for cloning or popping seeds, tap water will 99% of the time work best, but you will still want to pH it, cuttings and seedlings prefer a pH closer to 6.5 from my experience.

If your plants are wilting and dying practically overnight then its got to be a pH issue, and at that probably to low of a pH. Go to a local hydro store and pick yourself up a nice pH meter, its a must have tool for any gardener.

Truckn said:

This is interesting, never once did I consider it being too low. But Advanced advertises that their nutrients are pH fixing, when I did tech support they assured me that it to be a nutrient build up and told me to flush.


The cloner was not the first occurrence of this just the most recent. I have some pictures and documentation of it killing my big veg plants in my rollitup post from a year ago I can dig em up if it helps.

The ultimate conclusion I came to was there was some very rare toxin or pathogen entering somehow through the filtration process. So I just don't use it.

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To a statement made by another poster - you do not get a "super low" pH by combining two "low" pH solutions. Your pH will be as low (or high) as the lowest (or highest) solution used. Example: Water with a pH of 6 combined with nutes with a pH of 5 will yield a pH no lower than 5 and more likely someplace in between depending on the volumes of solution and diluent used. pH is not like working with positive versus negative numbers. It simply stands for the confusing term "power of hydrogen" representing the alkalinity or acidity of a given solution or substrate or mineral or yadda yadda. Hence an early poster stating it was like you fed them "straight soap" to obtain a pH that high when combined with the water you say is 6.0. If nobody else has said it - buy a GOOD quality pH meter and learn to use it, care for it and calibrate it. Then do all those.

If using advanced nutrients PH Perfect range you don't need to PH it at all! Just add to water and bam your away.

Truckn said:

When I was using the r/o water I was also using advance nutrients and that stuff is suppose to to have perfect pH. Whenever I tested it, I use the colored drops method which isn't the best it still came out a reasonable pH number.

Regardless of what additives were in the r/o water it would kill plants. Switching back to tap seemed to heel them and hasn't caused any harm since.

Click to expand...

Truckn said:

This is interesting, never once did I consider it being too low. But Advanced advertises that their nutrients are pH fixing, when I did tech support they assured me that it to be a nutrient build up and told me to flush.


The cloner was not the first occurrence of this just the most recent. I have some pictures and documentation of it killing my big veg plants in my rollitup post from a year ago I can dig em up if it helps.

The ultimate conclusion I came to was there was some very rare toxin or pathogen entering somehow through the filtration process. So I just don't use it.

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as far as i know, most.. if not all nutes have a buffer that decreases the ph..never raises it. the reason behind it is because it it very uncommon to have water come out of the tap above 7.0...which is nutral.Increaser would not be added because it would just counter balence itself, which would make it useless. if the ph get low, it turns acidic and does unnecessary damage to older water lines and some newer pvc kinds(cpvc). some citys have better filtration than others and it differs alot depending on what kind of climate u live in. this is fact and the only reason i know this is because ive worked at Rock MTN Colby Pipe co. for going on 11 years now and our QC does lots of tests in different PH ranges on different types of material. ive worked with several different types of Reverse Osmossis set ups from huge 1000 gallon ones and tiny 1 1/2 gallon ones and have never ever seen one backfire so bad it caused toxic water for plants. im not sayin i dont believe ya, because im sure ur plants died if thats what ya said...but I am saying 99.9% sure that ur R/O filter is working just the way it should and that up PH is botteming out due to the nutes. check it out and let me know cuz im curious about it now and im all about helping keepin a garden green!

hotrodharley said:

To a statement made by another poster - you do not get a "super low" pH by combining two "low" pH solutions. Your pH will be as low (or high) as the lowest (or highest) solution used. Example: Water with a pH of 6 combined with nutes with a pH of 5 will yield a pH no lower than 5 and more likely someplace in between depending on the volumes of solution and diluent used. pH is not like working with positive versus negative numbers. It simply stands for the confusing term "power of hydrogen" representing the alkalinity or acidity of a given solution or substrate or mineral or yadda yadda. Hence an early poster stating it was like you fed them "straight soap" to obtain a pH that high when combined with the water you say is 6.0. If nobody else has said it - buy a GOOD quality pH meter and learn to use it, care for it and calibrate it. Then do all those.

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i never said that adding 2 low ph solutions will make it "super low"..but what i did say is if is already low (6.0) and u add something that naturally decreases PH (like nutes), it will bottem out and become "supper low". the combo of the 2 will drop it below 6.0...gaurenteed

3/1 R/o and tap water?... That's what i do with my plants, Helps buffer and you get some of that calcium your plants love.

I only use RO water on my plants and clones and I dont add any ca mg I just add some carbon filtered tap water to the RO water along with my nutes. I feel this adds back in some of the ca and mg the plants need. I grow clone with easy, so far I have a 100% success rate and my plants are nice and healthy. Oh my RO water is at about 10-15 tds last time I check it.

I am trying a batch on tap water now. It doesn't devastate me too much when my clones die. It's when the plant is 5 weeks old looking real healthy then suddenly. In a matters of hours the leaves will do some crazy eagle clawing. Like the witches shoes from wizard of oz kind of curling. And the new growth will turn yellow then die. Out of nowhere.

I have flushed plants to get them at reasonable pH and PPM in case of nutrient block up. Or pH lock out, nothing seemed to save them.