RO membrane (in)efficiency question...

[Newreeflady]

I read that this membrane should give 5-10% of your original tds as the output. My input water is 33ppm and after RO it is still 12ppm... Shouldn't it be at like 3ppm?

(after DI it is 0, btw, but that isn't part of the question.)

Thoughts?
-A

 

[moonpod]

inadequate pressure and temperature variations as well as chlorine exposure can affect the membrane

 

[Newreeflady]

So, what am I supposed to check? I left a message for AWI and am waiting for response. The system is brand new (3 days old.)

-A

 

[Bryan89]

I would say that your water pressure is low. Are you sure the inlet is only 33 ppm TDS? That seems rather low.

Also, at 12 ppm out of the RO you are going to exhaust your DI resin very quickly

Bryan

 

[AZDesertRat]

How long have you let it run and did you dispose of the first water it made? I would let 20 or 30 gallons go through it before adding the DI cartridge to get the pickling/storage compound flushed out of the membrane.
At 12 ppm TDS you will get about 250 gallons per DI refill if you have the vertical canister type.

 

[BLockamon]

Also keep in mind that all the ratings of RO units are for 77 F water with an inlet TDS of about 250 ppm. If you really only have 33 ppm on the inlet, you probably have hard water, which will affect performance. In some cases, I have seen recommendations to add a water softener before the RO. I would ask the manufacturer and see what they recommend.

 

[xcreonx]

Very true, you need to run 30-40 gallons throught it and dispose of that water before you'll get 0-3 tds water. The Membrane has some kind of preservative on it that needs to be washed away.

 

[Newreeflady]

o.k. Well, at this point probably about 25 gallons have run through it. (and about 12-15 through the DI.) Obviously these are approximations. I emptied two tanks (total 6g) before running any through the DI.

Well, I have run more water through it and now the RO tests at 4ppm after letting it run for a few minutes (or test of the water from the storage tank.)

So, now, do I need to flush it or something? Did I mess up the DI filter? It is not vertical, but horizontal (I didn't get the information that the first was better before ordering)

Thanks for the help,
Angela.

 

[xcreonx]

if the ro tests at 4ppm before the DI, then you are good. The DI should clean the rest out. It should be 0 after the DI.

If your unit came with a flush kit, you can flush it when you want, but it really shouldn't need it yet.

Horizontal DI filters work fine. They just can't be refilled or recharged. You buy new ones each time. The big canister DIs are better since they are larger and can be recharged when needed, but you should be fine. I had a horizontal DI for many years. Never and problems.