Does anybody know if the reject water (brine) from a R/O filtration system can be safely used to water plants and grass?
Hate to waste this water every day.

 

Thats a good question. I know I wouldnt want to use the back-flush water from my softner (i tasted it and it was salty) but your R/O system is probably a diff story.

 

Don't see why not, it will have more of a concentration of impurities, but you should be good.

For most people it is simply easier to send the excess on its way.

 

I guess that depends on which minerals (and how much)your basic water supply has to begin with.
Low end RO water systems usually have a fixed reject ratio and depending on the supply, the reject stream can be pretty darned hard.
If your water supply is hard, (like ours) delicate and potted plants do NOT like being watered with it as the minerals build up and even form a crust in the soil.
Hardy in-ground plants and grass can likely tolerate a bit more since they occasionally get some honest-to-goodness RAIN which washes some of the deposits down into the soil.

Stan, RO water systems do waste a bunch of water but the plants REALLY like that soft stuff better.
Try it on grass first and see if it can tolerate it.

Not sure how humid an area you are in, but here in the Coastal Bend, A/C units dump a BUNCH of water out the condensate drains. Plants like that stuff really well.
It wouldn't hurt to blend the reject water and condensate if you run A/C units as much as we have to here.

 

Thanks for the answers so far.
We have very low humidity here as it seldom goes above 50% and more likely to be in the 30-40% range. A few weeks ago it was 17%
I know condensate water is about as pure as you can get, and some units can generate about 10 gallons a day, but we do not use A/C here. No need for it. No heat in the houses either.
Will give it a try on some grass and see what happens.

 

If I remember correctly, on my old system there was about 10 times the reject water as product. So the waste water would only have 10% more of the impurities in question. Not much. And since it is an RO system it is just "filtering" out the impurities and not adding anything, like salt for instance.

When watering plants, if you simply watered them with 10% more un-filtered water you would be adding the same amount of impurities as you would be with 10% less of RO waste water.

Seems like a meaningless difference. Water with the RO waste.

My experience was with purifying sea water, for my own use, aboard my boat at sea. So I didn't water any plants, but the raw water was heavily laden with impurities. It was a pain to keep the membrane working and in good condition.

 

Stan I hope this experiment goes better then your driveway incident.
I think you should be ok. Maybe try it on the neighbors yard first.

 

An RO unit removes everything except the H2O part of water. The water is that pure it is aggressive. It will "eat" copper pipes, kind of water with a pH of less than 7. I have seen commercial RO units the take the reject water and run that through another RO unit. This is done several times to get the most RO water possible and really concentrate the rejected contaminants to send to the sewer system.

A small home RO unit rejects lots of water. Raspy is like spot on with what it rejects.

Condensate from a AC is much like Distilled water.

Keith

 

Very similar but it can contain impurities, often small amounts of metal like aluminum or copper that can leach from the condensation coils. I found this out because as a Gunsmith I need distilled water in my bluing tanks, ANY contaminates can cause unwanted results in the bluing process.

I tried the condensate water out of my dehumidifier, looks crystal clear and certainly cheaper than the distilled water I was buying. I ended up with a pretty by product in a custom rifle I was building, little red flakes in the bluing almost looked like a very expensive metal flake paint job

Sad thing is that was not the finish I was looking for and had to remove it and clean out my hot tanks. Oh well, somebody has to be the test dummy every now and then

 

Condensate water doesn't seem at all like distilled water to me. It condenses from the atmosphere. So it must contain dust, smog, sulphur, pollen, smoke, or any other stuff that happens to be floating by at the time and gets trapped on the cold evaporator. On a house AC unit this could also contain cooking by-products, nicotine, and all sorts of interior chemicals. Then, as Lary said, it likely disolves some metal on the way out of the system or picks up more dust from the PVC drain tube along with whatever growth is sitting inside that wet pipe. Yuk. The only thing it likely would not have is chlorine unless someone was using that in the house.

 

I do stand corrected. Thanks Top and Raspy, I always thought AC condensate was like distilled water.

If interested I do have a booklet on my computer at work that we offer people regarding home treatment devices.

Keith

 

We have an RO-DI for our Salt water Aquariums. Yes, you can use this water to water grass and plants. Won't hurt them a bit. If you have a way to store the water or pipe it to the lawn, go ahead. As far as using it for drinking water or anything where you would use distilled water, no, don't use it.

 

Top just uses that dehumidifier stuff on his LEGGS now.

 

Yeah right!

 

Thanks again for all the responses. Your answers have given me a new idea. I am trying to save water which prompted my grass watering idea. Down where I live (Paradise) we do not have a constant city water supply like most of you, so most houses have at least one cistern. I have two, one quite large and is underground. The other is on top of the roof and this is what supplies water pressure for the showers, toilets etc.

The underground cistern is used as an emergency backup for the roof tank when the city supply fails. This cistern also feeds my R/O divice and supplies water for all my lawn sprinklers. Based on your answers I can see no reason why I canīt dump my R/O reject water back into this cistern. Every day their is a lot of fresh water added, (thanks to the sprinklers) so that alone should dilute any harmful deposits from the R/O. OK; maybe it could be argued that in time the stuff from the R/O could build up in the cistern, but I donīt see that with all the fresh water that is added daily. Any solids from the R/O should settle out to the bottom of the tank. Yes, I am recycling a minute (much diluted) amount of the R/O reject water back into the R/O, but donīt see that as a problem. Does anybody?