Rodi question

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Rpbustillo

Aquarium Advice FINatic
Joined
Feb 25, 2013
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Is the waste water that comes from my rodi completely useless or can I use it for my freshwater tank? Is it worse than tap water for my aquarium?
 
Is the waste water that comes from my rodi completely useless or can I use it for my freshwater tank? Is it worse than tap water for my aquarium?

RO takes all of the things that aren't pure H2O out of water. All of the components that make up the TDS/GH/KH go into the waste water. This makes the waste water unbelievably hard. Harder than diamonds or Wolverine's skeleton from X-men. No freshwater fish, from any body of water, anywhere, would like that water.
 
RO takes all of the things that aren't pure H2O out of water. All of the components that make up the TDS/GH/KH go into the waste water. This makes the waste water unbelievably hard. Harder than diamonds or Wolverine's skeleton from X-men. No freshwater fish, from any body of water, anywhere, would like that water.

If he has a TDS meter he can just cut it with RO to make it acceptable. But then that just ruins the point...
 
You can use any brand of filter that will fit your unit.

I would stick a TDS meter in it and see what it is... it might be fine to use in your FW tank depending on the rejection rate of your system and the hardness of the water going in. Many people collect the water and use it to water plants. I have even seen a couple of folks put the waste water line into the washing machine and use it to wash clothes (fill the washer with it instead of tap water). You could also mix it with tap water if you want to use it in the FW tank... that would reduce the TDS.

Bottom line, Unless the water going in is really, really bad, it would probably be fine for your FW tank. Most RODI systems produce 1 gallon of RODI water and waste 3 or 4 gallons, depending on how many membranes you have and the temperature of the water. That means at worst the waste water will be 25% higher in TDS than your normal tap.
 
Bottom line, Unless the water going in is really, really bad, it would probably be fine for your FW tank. Most RODI systems produce 1 gallon of RODI water and waste 3 or 4 gallons, depending on how many membranes you have and the temperature of the water. That means at worst the waste water will be 25% higher in TDS than your normal tap.

Really it's that minor? I always thought the waste water would be much higher in TDS than that. If it's only 25% higher that'd be great for, say, lake Tanganyika fish, assuming your tap water had a pH in the mid 7s and a gH and kH of 8 or so.. you'd end up with what, 8.2 or so and a gH and kH of 10 or 11? That's not too bad.

You learn something every day :)
 
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