Membrane In Ro Unit Help

[Chris_C]

I bought a second hand RO unit the other day after plumbing it in today i thought i would have a play.


My tap water is 31ppm TDS (Very low )

and after it has run through my RO/DI it comes out at 0


I have read on the the internet that even if it is 0 at the end it doesnt mean all is well with your unit.

i read that it is best to test the water before it gets to the DI stage so i took water from a pipe before it gets to the final DI stage and it was 7ppm TDS.

After doing the maths to work out the rejection rate i am getting around 77%


Am i right in thinking that the maths is ..

Tap TDS - RO TDS Divided by the Tap TDS x100 = rejection rate




So .. 31 - 7 = 24 Divided by 31 = 0.77419(etc..) x 100 = 77.4% rejection rate


Sorry for the maths lesson just want to make sure i am right before replacing the membrane.

 

[weezawoo]

Wow I just got a serious headache! haha! Surely you don't need to replace anything until the end result rises. Then I have been told the first thing to check is the DI resin, then the prefilters then the membrane?

 

[seffieuk]

Cricky that Maths made my head hurt and shut down!

The rejection should be:

1 part water to 4 parts rejection

To me, your membrane is working fine, you have 0 tds after the di resin and 7 before, with your tap water at 31, which is indeed very very low

Seffie x