# RODI "Waste Water"



## conjuay (Aug 18, 2012)

Hello,
I need to purchase a RODI system for my reef tank and am in the process of setting up a 65 gallon Freshwater as well. (Planted- of course!)

I am curious; would the water 'rejected' by the membrane of the RODI be suitable for the freshwater system?
It would have already passed three stages of filtration, including chlorine/chloramine filtering. 
I'm intending to do a blackwater system with (eventually) some discus, and they sound as if they might be as fussy as the reef critters.
TIA,


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## niko (Jan 28, 2004)

The waste water is not as dirty as you may think.

For each 1 gallon of RO water that you collect about 3 gallons of waste water are produced. Meaning that you have now taken tap water and removed 25% of the pure water. The remaining volume is now 25% dirtier than the original tap water. Sounds pretty bad but it is not. I've smelled and tasted that water and I have checked the TDS. It is barely higher than the tap water (if the tap is 250 the RO waste water could be 265, that's VERY little difference).

The problem with using the waste water for a fish tank is not the RO system that you own. It is the water company. They change the chemistry of the water depending ot many factors (weather, water plant mantenance etc.). What the RO system does for you is to remove whatever is in that tap water and give you always the same level of cleanliness. Using the waste water is just fine til the day when without warning the tap water comes much dirtier than usual. You may not even notice that but your fish will, especially discus.

That's all there is to it. Most of the time the waste water is perfectly useable. Water house plants, wash dishes - basically it is tap water. I have used it for years to water house plants with no ill effect (not even Chlorine burn). The easiest use of the waste water is to use it to water the trees in your yard - collect it and dump it around the tree, you are done. If you live in the US then the waste water from your RO is way cleaner than the water that comes out of the tap in many other countries.

By the way, since we are on the topic of RO and RO waste water: Do you know how much water is used to produce 1 (one) gallon of bottled drinking water? *About 8 gallons!!!* That's because of the RO waste water, and the water needed to make the plastic bottle. But most people love to look cool sipping on overpriced bottled water cause it makes them look healthy minded or something. It looks cool doesn't it?


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## conjuay (Aug 18, 2012)

I never thought of it that way. I assumed that because the RODI waste had already been through so many levels of purification, that it would be already cleansed of a large majority of the tap crap; having been filtered for both large particles and carbon treated twice. 
But that's why I asked, because it seemed too simple a solution!


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