Second RODI Membrane?

dooleyb · 01/31/2008, 06:27 AM

Has anyone added a second membrane to their RODI unit to recycle the waste water a second time to conserve water? I would like to know more about how it is done and how much water is conserved on the second pass.

Any feedback is appreciated.

cardiffgiant · 01/31/2008, 08:08 AM

Tagging along on this. I'm also interested.

I was thinking about running the waste line down to my washing machine, but I don't know if I could do that without opening a wall.

Roy G. Biv · 01/31/2008, 09:17 AM

The RODI that I have from the fiter guys does exactly that. I have a lot less waste water than before.

http://www.thefilterguys.biz/water_saver_ro_di.htm

AZDesertRat · 01/31/2008, 02:22 PM

The advantage of two membranes is to get more production in a shorter time. Waste or flush still needs to be maintained at the 4:1 level to keep the membranes flushed or they will fail prematurely. There are lots of studies on this subject and it has been proven time and again. There are units being sold as water savers but none has the long term testing to back them up. Manufacturers like Spectrapure have run units in their lab non stop for years and found it does not work.
The only true water saving RO/DI system today is the MaxCap UHE from Spectrapure which has some very unique microprocessor controls and flush systems to make it work guaranteed.

wife no likey · 01/31/2008, 02:47 PM

actually, I'm running triple membranes and am getting about 1.5:1 w/ about 220 TDS in and 1 post RO.

I do however have a fairly complicated flush mechanism incorporated that dumps the first minute of output down the drain as well as permeate and booster pumps.

Don't know if it's going to kill the downstream membranes significantly faster, but as long as I still get a couple of years out of them I'll be happy. I think that with my incoming TDS not being that bad, the minimal increase over the 2nd and 3rd membranes is going to be pretty inconsequential though.

It also is nice to start filling the Brute and have it filled in four hours (instead of overnight)

dooleyb · 02/01/2008, 12:19 PM

Thanks everyone for their feedback. The water pressure on my unit is between 30 - 50 lbs. What will a booster pump do? I know it will boost the pressure and keep it more consistent. Will it make more water in a shorter period which results in more waste? or does it reduce waste?

Roy G. Biv · 02/01/2008, 12:24 PM

Mine is rated for a minimum of 65psi. I have 60 normally. Most of the time it is fine for me, just less production. Depending on how high you set the booster, you will make more water. I have a booster when I need to make a massive amount of water. I set the booster at 100psi and get 1 TDS water. So there is a point where TDS will sneak through if it is set too high.

AZDesertRat · 02/01/2008, 01:01 PM

Take a look at this thread. Research has shown you not only get better production with a booster pump, you get better quality too.
http://reefcentral.com/forums/showth...readid=1234209

dooleyb · 02/05/2008, 06:00 AM

Thank everyone for their feedback and comments. I have been thinking about adding a booster pump but came to realize that increasing the water pressure would increase the pull down of the well water which could be a bad thing if the well is refilling slower than the pull off.

AZDesertRat · 02/05/2008, 08:05 AM

The increased production with a RO only booster pump might amount to 2 or at most 3 or 4 gallons per HOUR. I would not think a few gallons per hour would have any effect on your well unless it is a really low producer. Several gallons per minute might have an effect but not per hour. It might not even have any effect at all when you consider you will be reducing the waste volume due to the colder water by driving it through the membrane rather than to waste. You might even help the well situation.
I think you are thinking about a whole house booster pump not a little RO booster pump like the AquaTec 8800.

01/31/2008, 06:27 AM	#1
dooleyb Premium Member Join Date: Jun 2003 Location: Blacksburg, Virginia Posts: 555	Second RODI Membrane? Has anyone added a second membrane to their RODI unit to recycle the waste water a second time to conserve water? I would like to know more about how it is done and how much water is conserved on the second pass. Any feedback is appreciated.

01/31/2008, 08:08 AM	#2
cardiffgiant Registered Member Join Date: Apr 2007 Location: Tampa Posts: 3,455	Tagging along on this. I'm also interested. I was thinking about running the waste line down to my washing machine, but I don't know if I could do that without opening a wall.

01/31/2008, 09:17 AM	#3
Roy G. Biv Premium Member Join Date: Jan 2007 Location: New Jersey Posts: 3,646	The RODI that I have from the fiter guys does exactly that. I have a lot less waste water than before. http://www.thefilterguys.biz/water_saver_ro_di.htm

01/31/2008, 02:22 PM	#4
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	The advantage of two membranes is to get more production in a shorter time. Waste or flush still needs to be maintained at the 4:1 level to keep the membranes flushed or they will fail prematurely. There are lots of studies on this subject and it has been proven time and again. There are units being sold as water savers but none has the long term testing to back them up. Manufacturers like Spectrapure have run units in their lab non stop for years and found it does not work. The only true water saving RO/DI system today is the MaxCap UHE from Spectrapure which has some very unique microprocessor controls and flush systems to make it work guaranteed.

01/31/2008, 02:47 PM	#5
wife no likey Registered Member Join Date: Oct 2005 Location: Pittsburgh, PA Posts: 647	actually, I'm running triple membranes and am getting about 1.5:1 w/ about 220 TDS in and 1 post RO. I do however have a fairly complicated flush mechanism incorporated that dumps the first minute of output down the drain as well as permeate and booster pumps. Don't know if it's going to kill the downstream membranes significantly faster, but as long as I still get a couple of years out of them I'll be happy. I think that with my incoming TDS not being that bad, the minimal increase over the 2nd and 3rd membranes is going to be pretty inconsequential though. It also is nice to start filling the Brute and have it filled in four hours (instead of overnight)

02/01/2008, 12:19 PM	#6
dooleyb Premium Member Join Date: Jun 2003 Location: Blacksburg, Virginia Posts: 555	Thanks everyone for their feedback. The water pressure on my unit is between 30 - 50 lbs. What will a booster pump do? I know it will boost the pressure and keep it more consistent. Will it make more water in a shorter period which results in more waste? or does it reduce waste?

02/01/2008, 12:24 PM	#7
Roy G. Biv Premium Member Join Date: Jan 2007 Location: New Jersey Posts: 3,646	Mine is rated for a minimum of 65psi. I have 60 normally. Most of the time it is fine for me, just less production. Depending on how high you set the booster, you will make more water. I have a booster when I need to make a massive amount of water. I set the booster at 100psi and get 1 TDS water. So there is a point where TDS will sneak through if it is set too high.

02/01/2008, 01:01 PM	#8
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	Take a look at this thread. Research has shown you not only get better production with a booster pump, you get better quality too. http://reefcentral.com/forums/showth...readid=1234209

02/05/2008, 06:00 AM	#9
dooleyb Premium Member Join Date: Jun 2003 Location: Blacksburg, Virginia Posts: 555	Thank everyone for their feedback and comments. I have been thinking about adding a booster pump but came to realize that increasing the water pressure would increase the pull down of the well water which could be a bad thing if the well is refilling slower than the pull off.

02/05/2008, 08:05 AM	#10
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	The increased production with a RO only booster pump might amount to 2 or at most 3 or 4 gallons per HOUR. I would not think a few gallons per hour would have any effect on your well unless it is a really low producer. Several gallons per minute might have an effect but not per hour. It might not even have any effect at all when you consider you will be reducing the waste volume due to the colder water by driving it through the membrane rather than to waste. You might even help the well situation. I think you are thinking about a whole house booster pump not a little RO booster pump like the AquaTec 8800.