Do I need to replace the RO membranes on my RODI unit?

Daniel@R2R · Nov 11, 2016

I just moved, so the RO membranes in my RODI system haven't been used in months (it's a 200 gpd system, so 2 x 100 gpd membranes). I'm already planning to replace sediment, carbon, and DI resin, but is there any reason I need to replace the RO membranes as well, or are they good to go as long as I'm pulling the right TDS?

Alfrareef · Nov 11, 2016

Following.

Water Dog · Nov 11, 2016

If your TDS is up to spec for the membrane you have, I think you'd be good to go!

Antics · Nov 11, 2016

Was it stored wet or dry? I don't believe they are intended to be allowed to dry out. If it has been dry for months you should probably replace it along with all your other stages. If you plug it in and it seems to be working (the rejection rate from your base tap/well to the output before the DI) then you're probably good to go. I worry about everything so I'd personally just replace it for peace of mind.

Daniel@R2R · Nov 11, 2016

Antics said:
Was it stored wet or dry? I don't believe they are intended to be allowed to dry out. If it has been dry for months you should probably replace it along with all your other stages. If you plug it in and it seems to be working (the rejection rate from your base tap/well to the output before the DI) then you're probably good to go. I worry about everything so I'd personally just replace it for peace of mind.

They're actually still installed (so they stayed in their canisters with whatever water might have been in there). I kind of want to replace them, but then I look at that price tag for both of them...

Diesel · Nov 11, 2016

If stayed moist in the canister you're good to go... go... go

But just in case order a back up as with all your filters, great sales going on right now.

Randy Holmes-Farley · Nov 11, 2016

I'd check flow and TDS reduction before deciding to replace an RO membrane.

Daniel@R2R · Nov 11, 2016

Thanks guys! I'll test them and hopefully they're fine.

Buckeye Hydro · Jan 14, 2017

Two things to consider in your situation:
The RO membrane housing, depending upon how your system is set up, may not have been full of water, so at least part of the RO element may have dried out - if so, it will be ruined.
The other thing that always comes to mind is that you had that membrane "marinating" in dechlorinated stagnant water for some period of time. Perfect conditions for biofouling.

So if you open the membrane housing and the membrane stinks - you have biofouling - throw the membrane out and sanitize the entire system.

If the membrane doesn't stink, and as Randy suggested the rejection is still good, AND if the recovery is still good, you should be good to go. In this hobby people get to the concept of recovery via the "waste water to purified water ratio." Not quite the same thing, but close enough for what we're talking about here.

Russ

jason2459 · Jan 15, 2017

Why the sanitize part? Assume it's not for drinking and only for saltwater aquarium use.

Buckeye Hydro · Jan 16, 2017

Its good practice to sanitize your system at least once a year. Always a good practice to sanitize a fouled system, or one that has been setting idle for an extended period. The idea is to keep the new replacement filters from fouling.