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SSalty
03/02/2009, 10:39 PM
What is your water to waste ratio with your RO/DI? I just got a new 75gpd RO/DI at it seem like it waste a lot of water. Or maybe I am not use to a 75gpd membrane? Out of my waste line the water doesn't drip out, it just pours out.

TomRep
03/02/2009, 11:06 PM
should be a 1:3 ratio. 25% good water to 75% waste

MTB
03/02/2009, 11:10 PM
I have another question that kinda relates...

How do you correct the ratio if it is not right? Adjustable flow restricter?

stevenp
03/02/2009, 11:15 PM
I use a preset flow restrictor. My life became a lot easier once I added it.

SSalty
03/02/2009, 11:19 PM
<a href=showthread.php?s=&postid=14522552#post14522552 target=_blank>Originally posted</a> by stevenp
I use a preset flow restrictor. My life became a lot easier once I added it.

Can't you adjust the ratio by lower or raising the water pressure, or does this have no effect?

stevenp
03/02/2009, 11:36 PM
<a href=showthread.php?s=&postid=14522588#post14522588 target=_blank>Originally posted</a> by SSalty
Can't you adjust the ratio by lower or raising the water pressure, or does this have no effect?

I'm really not sure, but I imagine they'd maintain the proper ratio regardless of pressure. I run a booster pump which is set to maintain pressure at ~75psi and my ratio appears to be pretty close to 3:1.

TomRep
03/03/2009, 06:54 AM
The optimal pressure of an rodi membrane is somwehere around 70-80 psi if I remember correctly. so, you don't want to lower your pressure to try and get the correct ratio. If your flow restricto is not performing properly, you can either buy a new one (they are cheap) or use a ball valve with john guest fittings and set it up. If you se the ball valve method, it may need to be readjusted every so often.
tom

wboyden
03/03/2009, 07:34 AM
I'm really not sure, but I imagine they'd maintain the proper ratio regardless of pressure. I run a booster pump which is set to maintain pressure at ~75psi and my ratio appears to be pretty close to 3:1.

So you get 3 good to 1 waste?

LobsterOfJustice
03/03/2009, 10:55 AM
Remember your production will drop off a lot in cold weather.

TomRep
03/03/2009, 11:51 AM
another good point. RODI membranes work best with (I think it is) 77 degree water or something like that. however, hit 79-80 (again, i believe these are the numbers) and it can kill the membrane.
tom

Jerm77
03/03/2009, 12:26 PM
I don't think a flow restrictor is the best way to go about it. it is possible to damage the RO membrane. I think a better way is to tightly coil up your brine(waste) line until you get the desired waste ratio. I would say an average waste ratio is 1:3. but you may want higher if you have really hard water.

stevenp
03/03/2009, 11:23 PM
<a href=showthread.php?s=&postid=14523782#post14523782 target=_blank>Originally posted</a> by wboyden
So you get 3 good to 1 waste?

No, 3 parts waste to 1 part filtered.

MTB
03/08/2009, 08:16 AM
<a href=showthread.php?s=&postid=14525448#post14525448 target=_blank>Originally posted</a> by TomRep
another good point. RODI membranes work best with (I think it is) 77 degree water or something like that. however, hit 79-80 (again, i believe these are the numbers) and it can kill the membrane.
tom

Yeah, I've read that too. I hooked my supply line up to the cold water supply. I stays around 60* f. How can I get the temperature to come up? Even in the summer the cold water stays around 60*. My ratio is around 1:5 right now. I'd like to get around 1:3 so I don't needlessly waste water. I have the BFS 75 GPD premium system.

wboyden
03/08/2009, 09:11 AM
the only problem I can see with raising the temp of the supply is that you only have a small amount of temp to play with from what I have seen and has been posted here that 77 is the best temp but 2 degrees more and you can kill it.

Now, I am really new at this and have only been looking at these for a couple weeks but I say adding a coil of tubing to a heated tank could raise the temp a few degrees.

Adding some sort of inline heater I think would get the water too hot.

I have also read somewhere that the rejection rate also has something to do with how high your tap TDS is and how hard or soft the water is.

Would adding an additional pre-filter or water softener help.?

JCJHET
03/08/2009, 10:07 AM
If not enough concentrate is allowed to flow past the membrane the impurities will precipitate on the surface and clog the membrane.
Anywhere from 4:1 TO 6:1 waste to product is normal. This is at 60 psi 77 F. 40 to 80 psi is acceptable and most units need to stay under 100 F.
Flow restrictors are the best way to adjust the ratio.
A softener will increase membrane life.