# RO reject water use...



## gtrewjr (Feb 4, 2006)

Can you use your RO reject water for anything or is the mineral content too high for use?

My tank is setup in the front part of the house and I live in an old style pier/beam type of place so I have crawl space below. I was thinking about re-routing my reject line to a flower bed at the front of the house. Any thought on this? Or just a plain bad idea?

Thanks for your comments.

Grady


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## yoink (Aug 31, 2005)

I have heard of people using the waste water to water their flowers and other terrestrial plants. I would think the high mineral content would be good most outdoor plants.


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## Laith (Sep 4, 2004)

Some people use the reject water to mix back in with the RO water to get the GH and KH they want...


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## jbierce (May 11, 2006)

I wouldn't advise mixing wastewater and purified water together. Without a good analysis of your tap water it's hard telling what minerals are making up that GH; which isn't something you have to worry about when you're adding the minerals yourself.

You can use the wastewater for plenty of things though, including watering your plants outside. Around 90-98% of the TDS is present in the waste, but the waste also makes up around 80-90% of the total water that goes through the system. In the end the mineral content of the waste isn't all that different from normal tap water. If you have to pay a water bill, it's a good idea not to waste any. Investing in a permeate pump will also help a lot in reducing waste.

JBierce


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## Laith (Sep 4, 2004)

Most people cut their RO water with tap water to get the GH and KH levels they want. Using the waste water from the RO unit just means you need less of it as it's more concentrated.

The only time I'd recommend against this is if you are one of the rare people who has really strange tap water with for example extremely high heavy metal content (and that's why your using an RO unit in the first place).

GH is a measure of Calcium and Magnesium... it is not the same as TDS. What varies between tap waters is the proportion of the two that are making up the GH.


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## jbierce (May 11, 2006)

Actually, GH is a measurement of several metallic ions. Iron, strontium, barium, copper and zinc among others also affect your overall GH reading; just not nearly to the degree that calcium and magnesium do. That's mostly moot though, since there's no way to separate your GH minerals from all the other compounds in your waste water. If you add 50% of your waste water back in to correct your GH, you're also placing 50% of everything else in. That was my point.

Also, it's not all that rare to have heavy minerals in your tap water; especially if you live in the big state of Texas.

JBierce


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## hooha (Apr 21, 2005)

Would you be able to use waste water for fish-only tanks?

Also what is a permeate pump?


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## jbierce (May 11, 2006)

It depends on what minerals and compounds are in your tap water. In some areas the tap water in unsuitable for fish, so the waste would be even worse. This can be anything from high copper levels to high nitrates. Although copper shows up on your overall GH reading, even an extremely severe amount wouldn't affect the GH that much. Only a good analysis of your tap water would show if it would be safe. For example, if the nitrate level in your tap water is 10ppm, it's going to be higher in the waste due to the high rejection rate of the membrane. That's an unacceptable amount of nitrate to add to your water.

A permeate pump increases the pressure on the waste side of the membrane and decreases the pressure on the pure side. It boosts efficiency of the filter by up to 80%; especially if you're running your filtered water into something that produces back-pressure.

JBierce


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## Steveb (Oct 20, 2005)

I just hate to see all that water go down the drain, so I store both my RO water and waste water in barrels.

I use my waste RO water in my African tanks, livebearer tanks, rainbow fish tanks and grow out tanks for cory's etc. My tap water is pretty good (7.5 pH, 3KH 3GH). My RO unit makes about 50 gals of RO water and 150gals of waste. This is with a pressure pump and no restriction on the RO output, my tap water is pretty cold so that reduces the RO output some. I've been using this setup for about 4-5yrs now, no problem so far. 

SteveB


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