RO/DI filter change?

[obscurereef]

The tds from the RO/DI water is reading 6! Is it time to change the filters, and what should I change? Just the DI resin, the carbon, everything? Thanks

 

[Phranque]

At minimum, it's time to change the resin. What is your RO only TDS vs the tap water TDS? This will tell you when it's time to change the membrane. If you're getting much below 95% rejection rate, then I'd change it. Otherwise, you'll be chewing through your resin much faster. My tap TDS is around 450, and my RO TDS is 9 (98% rejection rate), so I'd change my membrane at about 20-25 TDS.
IMO, canisters (sediment & carbon) should be changed every 3 to 6 months, depending on usage.

 

[obscurereef]

I don't know...how do I find out just the RO TDS? Do I just take out the resin and run it that way to test?

 

[RickkyBobby]

Just move the tds meter to the line coming out of the ro membrane but before going into the di resin canister.. Thats it..

 

[Phranque]

I don't know...how do I find out just the RO TDS? Do I just take out the resin and run it that way to test?

Well, for future reference, you can do one of two things to make your life a little easier....

First, cut the line going from the membrane housing to the resin canister, insert a T with a valve line which enables you to pull RO only water.... this is what I use for freshwater blending so I'm not wasting resin. You can use this as a sampling line.

OR, pony up $25 and go to BRS on one of the bulk buys & get yourself a digital dual inline TDS meter.... aside from the 150gpd upgrade, this is one of the best purchases you can get for your RODI system.