RO system help

Black Phantom · #1 07-09-2009, 01:38 PM

I just replaced my RO membrane a month ago. Today I tested the water and to my shock it's over 100 TDS. I've confirmed this with an inline and handheld unit. I'm at a total loss as to whats happened. I have two sediment pre filters as well as two pre carbon filters as well. They still look good.
It's always easy to see an exhausted sediment filter but mine are only partially dirty. They were all replaced new with the membrane.
In the past I have always gotten at least 8 months out of a filter.
Any ideas out there?

Stupid filter

Black Phantom · #2 07-09-2009, 02:06 PM

Okay, I just found this thread on another site.

Check Valve: A check valve is located in the outlet end of the RO membrane housing. The check valve prevents the backward flow or product water from the RO storage tank. A backward flow could rupture the RO membrane.

This is a new one on me. I know I don't have one on my system. Does anyone else?

mike31154 · #3 07-09-2009, 04:30 PM

What is your source water TDS, just for comparison purposes? I do have a check valve at the outlet of my RO membrane as well as an auto shut off manifold downstream of that. Then there's the restrictor on the waste water line which must be matched to your membrane, whether it be 50, 75 or 90 gpd. My system has an integrated valve to enable flushing of the membrane. You may already know this, but perhaps it's worth double checking that your new membrane matches your restrictor. You may also want to ensure that your membrane is properly installed and seated. From what I've read, a membrane should last at least a couple of years.

Black Phantom · #4 07-09-2009, 05:03 PM

I'm on Calgary water which is pretty hard but tons of reefers use it. I ordered my new membrane and restrictor from J&L and double checked to make sure they match.
I'm wondering if without a check valve, and evertime I use my RO water tap from my holding tank I have been pushing water from my DI resin back into my membrane and have plugged it up. The wierd part is that I have had this system for over five years with no problems until now. The only thing new is my membrane and my holding tank that I purchased from Home Depot. (the old one died)
I also have the flush kit.

mike31154 · #5 07-09-2009, 08:07 PM

Well, I'm all out of ideas. Only thing I can think of in a situation like that is to look at the things you recently changed once again. If it worked fine for 5 years without a check valve, then I'd suspect the latest changes to your system. Can't really picture how your holding tank set up could be the culprit though.

Black Phantom · #6 07-09-2009, 08:46 PM

Well I think I tracked it down. About two years ago I changed the housing for my membrane and put new fittings on it. I dug the old one out of a drawer today and guess what? - yup - a backflow valve cleverly disguised as an elbow fitting

And at the same time my holding tank was wearing out but I never bothered to replace it until a couple of months ago. I guess there was never enough back pressure to force it's way back into the membrane until I installed the new one.
Ah well, live and learn............. and spend more money

mark · #7 07-09-2009, 10:45 PM

have a Aqua-safe unit and just took a look and there's a metal coupling between the housing and elbow (on the blue line side by where the arrow points to 4th stage membrane housing in the diagram), assume this is the check valve being mentioned?

mike31154 · #8 07-10-2009, 03:11 AM

Dunno, but my check valve is hard to miss, after the elbow, plumbed into the blue line separately, before the four port auto shut off manifold. It has an arrow on it denoting flow direction.

mike31154 · #9 07-10-2009, 03:15 AM

Quote:

Originally Posted by Black Phantom

Well I think I tracked it down. About two years ago I changed the housing for my membrane and put new fittings on it. I dug the old one out of a drawer today and guess what? - yup - a backflow valve cleverly disguised as an elbow fitting

And at the same time my holding tank was wearing out but I never bothered to replace it until a couple of months ago. I guess there was never enough back pressure to force it's way back into the membrane until I installed the new one.
Ah well, live and learn............. and spend more money

Ha, ha, long live pack rats. Good thing you stashed that stuff away vice turfing it. Hopefully you're good to go now.