View Full Version : RoDi

04-05-2010, 10:35 PM
I was just wondering if everyones RODI wastes as much water as mine I go through probably 10 gallons of waste water to make 5 clean. Is there any way to slow down the waste water????

04-05-2010, 10:38 PM
There exist zero waist systems (and retro kits) that feed the waste water back into your hot water tank I believe. Or you could get another storage bin and use the waste water to water plants and such.

04-06-2010, 01:23 PM
If your good to waste ratio is 5 to 10, then you're doing very well, since that's a 1 to 2 ratio! Most RO membranes are designed to operate on a 1 to 4 ratio, which would in your case be 40 gallons of waste water to the 5 gallons of pure.

At any rate, I collect all the waste water as kien suggested in large plastic drums. Use in garden in summer and for toilets in winter. Folks with top loading washing machines often use the waste water for laundry. I have a newer front loading washer and it uses very little water, not feasible to fill with RO waste. I plan to replace my hot water tank soon with an on demand, tankless water heater and I don't think that will work with the system that diverts RO waste back into the hot water system. There are also RO systems which add a second membrane to recirculate some of the waste and improve the ratio that way.

04-07-2010, 03:24 AM
... you could get another storage bin and use the waste water to water plants and such.

Be really careful if you do this, many plants won't tolerate the extra minerals in the water (guess where all those browned leaf tips and edges comes from). Using it for household stuff is a better option...

I am under the impression that there are booster pump systems that recycle the waste water back through the RO membrane or something, thereby reducing waste water. Maybe I'm imagining something that doesn't exist, or...?

04-07-2010, 03:52 AM
Google 'zero waste ro systems' and you will find a number of different approaches to cutting down the amount of waste water. All have pros & cons. Three main ones are pumping waste back into house hot water system, recirculating waste back through the RO membrane and permeate pump.

04-07-2010, 05:30 AM
The more expensive systems are closer to 1:1 good:waste. That's still 50% going down the drain and for the extra $$, you'd have to waste a HELL of a lot of water to make up the difference. If cost isn't your only concern (good for you) then your options are really only those already mentioned (all of which are of limited value and are generally a PITA !).

04-07-2010, 07:17 PM
you have to have waste for your membrane to work properly