RO/DI info

[tom reilly]

Still moving on with my 125 slow motion set up. another question. Some but not all of the RO/DI set ups mention waste water. Do they all produce "waste" water? How much waste water are we talking about to get 150 gallons of water for a tank start up?
Thanks in advance.

 

[bobman]

Yes all rodi setup produce waste water. The amount of waster water will depend on the system itself. That is from the ro membrane so if your membrane has a 90% rejection rate to get 150 gallons of rodi water it is a lot of waste water. Some use it for watering plants and such so it dont go completely to waste. But yes they waster a lot more water than they produce.

 

[tom reilly]

So I look for lowest rejection rate?Will having a water softener up stream help with this?

 

[redfishbluefish]

On a "standard" RO/DI unit, your waste to good water is about 3 to 1.

I use my waste water for the washing machine, and in the summer, for watering the plants. I have a 55 gallon drum for waste water.

 

[tom reilly]

Yes all rodi setup produce waste water. The amount of waster water will depend on the system itself. That is from the ro membrane so if your membrane has a 90% rejection rate to get 150 gallons of rodi water it is a lot of waste water. Some use it for watering plants and such so it dont go completely to waste. But yes they waster a lot more water than they produce.

 

[PatW]

A water softener replaces Ca and Mg ions with Na ions. So you still have the same amount of foreign stuff in the water. I don't know if water softener affects ions of Fe, Cu, Pb and other metallic ions. I would think that the RODI would still work just as hard removing the pesky Na ions.

 

[tom reilly]

Yes all rodi setup produce waste water. The amount of waster water will depend on the system itself. That is from the ro membrane so if your membrane has a 90% rejection rate to get 150 gallons of rodi water it is a lot of waste water. Some use it for watering plants and such so it dont go completely to waste. But yes they waster a lot more water than they produce.

Has the waste water been altered?

 

[bobman]

As far as what is in it I will let AZdessertrat chime as he is the rodi master but I think it is just tap water thats gone through the sediment filters and the carbon block so IMO it might be a little cleaner than your tap but I am not positive on that.

 

[mcarroll]

As far as what is in it...

More like what's out of it.

As you noted, prefilters and carbon would give the tap water a "Brita-like" cleaning.

But it's also had a pass through the membrane housing, so a percentage of the water's H2O molecules (and a few other things) have also been taken as "permeate" - or "RO water".

As a result, the wastewater is slightly concentrated, with a higher TDS. Great for most "greywater" uses....probably better than some tap water for drinking but I don't think I'd drink it.

 

[redfishbluefish]

Your waste water will have the "TDS" that gets stripped out by your membrane. The actually increase in TDS of your waste water is dependent on the efficiency of the membrane (ideally 98% or better), and your waste water ratio to good water. For most systems you're looking at a 20-25% increase in TDS with the waste water. For me, with raw water at around 175 TDS, I end up with waste water at around 230. That is still "drinkable." However, with some in the country with high TDS to begin with (greater than 700), I won't drink it out of the tap to begin with!

 

[tom reilly]

I guess when i fill the first time the yard gets watered real well.
My dry rock came today so i have stuff to play with.
Ro/Di filter is next purchase.

 

[bobman]

With a 75 GPD membrane it took me almost a week to fill my 150 and 50 gal sump. Mainly because I would turn it off when I went to sleep if the container was half full or better.

 

[Raddock]

BRS has an upgrade kit that allows you to run the waste from one membrane through a second membrane. This doubles your output and decreases your waste some. If you are looking for a complete setup they gave this as a complete system as well

 

[AZDesertRat]

Dual membranes ARE NOT water savers. Dual membranes give you more GPD if you have 65 psi or more at the tap but do not believe the water saver bunk, it's not that easy. When you send the concentrated brine from one membrane into another it is even more important you keep the waste up or you spend much more on unnecessary membrane replacements.

 

[FishOfHex]

Still moving on with my 125 slow motion set up. another question. Some but not all of the RO/DI set ups mention waste water. Do they all produce "waste" water? How much waste water are we talking about to get 150 gallons of water for a tank start up?
Thanks in advance.

Your looking at 3 gallons of waste to 1 gallon of RO and sadly not much you can do about it. I like to use my waste water for the garden.

 

[AZDesertRat]

The waste can be adjusted depending on the calcium carbonate hardness and TDS level of your tap water. With softened water and lower than normal TDS it is possible to reduce the waste to as low as 2:1 and still get good RO membrane and DI resin life, if the water is hard and TDS high then it is better to stick with the manufacturers recommended 4:1 waste ratio. It comes down to cost of ownership, if you want good filter life and a low cost of operation, about 5 cents a gallon on average nationwide, stick with what matches your tap water conditions, if you start cutting waste with hard water the cost per gallon goes up accordingly due to more frequent replacements and the quality of th eend product can go down.
The waste really isn't wasted though, it can go to the sanitary sewer system, be recycled, recharged and used over and over.