Old and New RODI 2PPM


New member
Ok so I just changed all the filters including my membrane on my 4 stage rodi.
and I’ve let the water run well over 3 hours, And my built in tds meter if giving me a 2ppm reading.

What could be going on? Before I was getting a 0ppm before I started to get 4ppm and then replaced the filters.
im about to just give up, Ive done pretty much everything i can. I even bought a brand new ROdi system and a brand new TDS reader. And the new system is showing 4ppm after, i followed the instructions and i have a higher tds reading on the new system now.

I also got a manual tds reader and it showing 3-4ppm with the new and old RODI units. Im using the same city water as before i used to get 0ppm until i changed my filters and now i cant get it down to 0ppm.

Also tested my incoming tds is reading at 193ppm and before going into the DI tds is reading 2ppm. Manual tds is reading 5ppm.
Temperature is 25c and i believe its city water. Water pressure is 60psi with out the boster pump and 100psi with boster pump.

Also made sure the resin was fill and packed tightly.


Premium Member
If you have 2ppm going into the Di but still have 2ppm coming out, it has to be something up with that stage. Bypassing somehow? Lines reversed? I doubt you have the cartridge inverted but I'll throw that out too. Are you using mixed bed resin and not just anion or cation?

Can you supply a picture of what the setup looks like?


Crab Free Zone
Premium Member
Had this problem just a week ago.
Turned out that my DI stage got somehow plugged and even though it was moving through the stage, it wasn’t passing through DI.
In my case, clean the DI canister fully, repacked, and went right to zero.