Replacing RODI Membrane

[newenglandreef]

Any idea how to tell when a membrane is spent? I purchased a used RODI about two years ago--I'm assuming it's about ready to replace, but I don't have very hard water-- 80 or so TDS. The membrane is presently a very light copper color.

 

[dannyp02908]

I have a pressure guage and dual inline TDS meter. When pressure drops, i change my 3 pre-filters. I monitor the TDS before and after DI. If before DI TDS increases, i change the membrane. If after DI TDS increases, I change the resin.

 

[newenglandreef]

Thanks, is that for the filter or for the membrane?

 

[dannyp02908]

Thats for the whole system. The pressure guage monitors the presure going in to your RO membrane after the prefilters. If you see the pressure decrease (and not because you turned on a sink or flushed the can), then you pre-filters are clogging. Time to change them. The dual TDS meter and 2 inline fittings. One goes after the RO but before the DI. The other goes on your product line after the DI. The before DI will usually read a little TDS. If you see that creeping up over time, then the RO Membrane is starting to go bad. After DI, it should always be 0 TDS. Anything higher, and your DI resin is exhausted. Time to replace. Keep in mind, when you first turn the system on after it has been sitting for a few days, its not uncommon to see a high tds before DI (after RO). A flush kit will take care of that so that you dont blow through DI Resin. All of the things i mentioned (pressure guage, dual inline TDS meter, and flush kit) can be had from bulk reef for around 50 bucks total if you dont already have them.

 

[dcforester1]

Are you talking about changing the membrane or DI resin? The membrane doesn't change color, the resin does. Some people write on the side or in a notepad how much water they make and go by that. I bought a 6mo old system just about 3 yrs ago and I am still on the same membrane. Just last week I was getting 2TDS, and I really thought this was it, but I changed all the pre filters, and the resin and I am back to 0. I only have about 78TDS going in, but the membrane has lasted awhile.