How often do you change your RODI media?

akabryanhall · Feb 26, 2011

How often do you find you have to change your RODI media?

Alpha Aquaculture · Feb 26, 2011

It is different for the different filters. Usually the DI gets replaced much more frequently. I would call up the manufacturer of your RODI and ask them how often and what signs to look for to know when to change. I was told by my RODI manufacturer that many things can influence how often the filters have to be replaced. The quality of the water your filtering has a lot to do with the frequency of filter replacement.

akabryanhall · Feb 27, 2011

Thanks man, that clears up a lot! I think its about time to change mine, It is in a spot that gets sunlight unfortunately.

swannyson7 · Feb 27, 2011

I don't change them as long as the in-line TDS meter reads zero

AZDesertRat · Feb 27, 2011

Prefilters and carbon blocks have very little to absolutely nothing to do with TDS, they are there to protect the RO membrane from large sediment and particulates, suspended solids not dissolved solids, and chlorine.\

You change the prefilter and carbon every 6 months like clockwork regardless of how much or little water you have made. Remember, all water passes through these first filters including the waste so you have passed at least 5 times as much water through them as you have treated. You should also disinfect the system at this time since you already have it out of service and disinfection takes like 5 minutes.

You change the RO membrane when it is no longer cost effective to keep changing DI resin or cartridges, usually when the rejection rate has dropped to maybe 94-95% depending on your tap water quality. A good rule of thumb says for every 2% your rejection rate drops it cuts your DI life in half so the difference between 96-98% and 94-95% is quite dramatic and you recover the cost of the new membrane quickly if you make much water.

You replace the DI resin or cartridge when the final RO/DI TDS is anything other than 0 on a consistent basis. If after running a few minutes the TDS does not drop to 0 its time for a change.

You need a TDS meter if you do not already own one, handheld meters are better than inline meters since you can use them portable and test not just two dedicated places. You need to know your tap wate rTDS, RO only TDS and RO/DI TDS so that would require two dual inline TDS meters but only one handheld. That plus the handhelds are more accurate since most like the HM Digital TDS-3 or TDS-4 are temperature compensated unlike the inlines. The reading can be significantly off if your water temperature and air temperature are not exactly the same and they rarely are.

akabryanhall · Mar 3, 2011

Hmm I may have to add a tds meter to my refractometer order.

Rayzback · Mar 3, 2011

Picked up a HM Digital Handheld TDS-3 Meter about month ago in order to test my RO/DI water. I had been replacing my filters based on an estimated expiration date which I am betting was sooner than they needed to be. I tested the water before the RO (117ppm), after the 5 stage RO (2ppm), and after the 2 stage DI (0 ppm). All in all, I'm happy with the purchase.... afforable, fast, and easy to use.