RO/DI unit working bad

[ReefCresteds]

OK My RO unit is officially working terrible. It is about 2 years old, 5 stage RO/DI. I have replaced the chambers 1,2,3 and refilled the DI several times. I just recently even replaced the 1-3 filters again thinking that was making it work so bad. But it's still the same. I get maybe 10-12 gal a day out of it? I run it all day/night. It's just a constant drip. I've taken the line off and I can't see anything clogged. I do put a plug on the end of the wastewater that only allows a drip/small stream to come out the waterwater end. As recommended by my LFS-is this good or bad?
Any thoughts?
I've never done anything w/ the 4th stage-the one I can't see into that runs horizontally on the top, below the DI.

Any thoughts on what I should do? Maybe I just need to get a better unit. It has worked much better in the past.

[wakesetter]

maybe replace the membrane. What is the tds of the water coming out of the product line? The horizontal piece should be your RO membrane and it may be toast decreasing your output and more importantly your quality.

[auckreef]

Firstly, you should unplug the outlet of each stage in turn, starting with the first (nearest the tap) stage, and run each one, to see where the blockage is. Also, unplug the inlet to the first stage & run the tap to see if there is a blockage before the water even gets to the unit.
As the first stage is presumably the coarse filter there should be little / no drop in pressure caused by it. Shouldn't be too much from the carbon block filters either. Assuming all this checks out, it must be the top one, which i THINK will be the RO membrane.
But just test each one individually to isolate where the problem is.

[Blown 346]

I agree with others, I would also un plug the waste water end and let it flow normally.

[ReefCresteds]

Thanks for the thoughts. Yea the first 3 chambers fill up really fast. So I don't think it is them. The TDS was reading I think around 10-15 last time I checked. It used to read like 3. So if it is the membrane where do I get a replacement for that just at a hardware store?

[Toddrtrex]

Is that TDS reading after the RO part or after the DI part?

Either way, is seems to me that your RO membrane is done, which would make you go through your DI a lot faster.

I recently replaced mine RO membrane, got it from the filter guys -- or any other of the sponsors would be a good place to go. All seem really helpful.

[Blown 346]

You will probably have to go thru the filter guys like suggested or a place that sells RO units to get the right replacement Membrane.

[wakesetter]

you can not just undo the waste water flow restrictor. It is a key part of the system. you need a certain amount of backpressure on teh membrane for it to work properly. I would call custom aquatic or visit them online and order a new membrane from them. At the same time replace the flow restrictor. They can go bad over time and they are cheap to replace. I always replace them together. They must be matched to the same flow rate as well. If your TDS has tripled or better, you need to fix something. Again, call Custom aquatic and ask for Todd. No affiliation here, just someone who has helped me out alot.

[AZDesertRat]

If you have plugged the waste line until it is just a drip you have undoubtable damaged the RO membrane. It requires a 4:1 waste ratio to keep the contaminants flushed away from the membrane, that's 4 gallons of waste to one gallon of good. I would venture to say you have solids built up on the membrane and it is shot.
Start over with a new 75 GPD membrane and matched flow restrictor or a capillary tube type restrictor which can be trimmed for an exact 4:1 ratio.
Prefilters and carbons have no effect on final TDS, its the membrane and the DI that take care of TDS. The pre and carbon are there to protect the membrane so it can do its job.

[ReefCresteds]

Excellent help everyone! Thanks-I will check on this today.

[nhlives]

Put a post on http://www.newengland.reefbuilders.com.
RJDudek on this forum sells these things and has some pretty good insight.

From what I have heard him say, your problem sounds like input pressure. But I would ask him.