Hooked up my RO DI, does this sound normal?

[Redbellyjx]

I was testing my water at three locations. 1)Tap. 2)Rejection point. 3)DI.

I have pretty good tap water. it measures 50 ppm. How ever, at the rejectiopn point, the water registers 65-70 ppm. but once going through the DI filters, it registers 2-3 ppm.


is it normal for it to be higher at the rejection point (the drain) than the inlet point?

 

[JMeesh]

if it goes in at 50, then yes the rejected water should be over 50. it is after all where the waste goes. the filter is moving it from the "supply" water and into the "waste" water. id think you would get more than 70 there though. also, id think you would get 0 readings after ro and di filters.

i just tested mine (thanks lcashman!) and it was 360 at the tap. 578 in the waste water and 17 after just ro....no di stage. this is just with the basic 3 stage coralife filter. its got a sediment filter, carbon block and the ro membrane itself.

im far from a guru though. good luck!

meesh

 

[mcurl98]

yeah, the waste water is going to be higher than the tap. You should be getting a 0 reading after the DI.

 

[Redbellyjx]

yea its reading 0 now. i guess i needed to make a few gallons first to clean out the system or something.

i bought a 6 stage filter


thanks, i was a bit confused on why the rejected water was higher than the tap

 

[Colin]

It would be a good idea to measure it after the RO but before the DI. That'll give you an idea of your membrane's rejection rate.

--Colin

 

[AZDesertRat]

You need to measure from 3 points but its the tap water, RO only before DI and finally RO/DI. Your waster stream is always going to be 20 to 25% higher than the tap water since you have a 4:1 waste ratio and that is carrying the concentrated waste away from the membrane.
You need the Tap and RO only to determine your RO membrane efficiency, thats the workhorse of the system and does 98% of all the work, if its not giving you at least 96% rejection and prefferably higher then it needs replacing. Any unit should be capable of giving you 0 TDS after DI they key of fo how long. Lesser quality units that have less efficient membranes pass more contaminants on to the DI resin so it exhausts faster and costs you much more money in the long run. Better membranes make the DI last longer since it does not have to work as hard and saving you money in the process. It pays to buy the best quality RO DI unit and replacement filters you can.