RODI Problems

C-Reefer · Jul 18, 2019

Hey guys
I just got a new to me (aka used) Spectrapure 5 stage Maxcap 90gpd RODI unit.

I immediately replaced the sediment and carbon block filters, but the owner said the RO membrane and DI resin should be fine. I hooked it up and something I've never encountered with an RODI unit happened. Water came absolutely rocketing out the waste water line and there was maybe 1 drop ever 2 seconds out the good water line. the di resin compartments did not fill up with water either. Supposedly water is coming into Membrane at 200 tds, and coming out at 15-20. Goes into DI at 15 comes out at 0. however I'm not getting good water. The pressure gage in RO unit is sitting at 10 but my water pressure out of the spigot is around 60.

I know that its a high porportion but the RODI units before this have had a good ratio. Something is not working right with the RO membrane/compartment. As an experiment I put my thumb over the waste water line and pressure shot up to around 65 and water came out of the good line at the rate I was expecting from previous RODI unit experience. However DI resins still did not fill up but the inline tds sensor said water coming out of DI was 0. I'm baffled.

This is just with water on. Only a few drops comi g out of the good water line.

Magnus042 · Jul 18, 2019

Does it have a backflush valve installed? Mine does that when im flushing it...

Opus · Jul 18, 2019

Check the flow restrictor, sounds like it may not be installed properly. If that isn't it, then it could be the RO membrane is going bad. I would expect your tds after the membrane to be in the 4 to maybe 8 range.

C-Reefer · Jul 18, 2019

Magnus042 said:
Does it have a backflush valve installed? Mine does that when im flushing it...

Im not sure but I don't think so. From what I can tell all tubing is correct too.

Opus said:
Check the flow restrictor, sounds like it may not be installed properly. If that isn't it, then it could be the RO membrane is going bad. I would expect your tds after the membrane to be in the 4 to maybe 8 range.

What is a flow restrictor and is it needed? I dont think I have one. I also have replacement RO membrane and DI resins.

MTBake · Jul 18, 2019

Sounds like it's missing the flow restrictor or the flush valve is open.

C-Reefer · Jul 18, 2019

MTBake said:
Sounds like it's missing the flow restrictor or the flush valve is open.

What is the purpose of a flow restrictor? Obviously to restrict the flow but does it restrict flow coming out of the waste line to raise water pressure? Or something along those lines?

MTBake · Jul 18, 2019

C-Reefer said:
What is the purpose of a flow restrictor? Obviously to restrict the flow but does it restrict flow coming out of the waste line to raise water pressure? Or something along those lines?

That's exactly what it does. Without it, water won't make it to the ro membrane. It will go out of the waste water line instead. There is 2 different styles of flow restrictor. The barrel type, which is large and obvious. And the capillary type, which you would need to remove the tube from the fitting it's installed inside of to see if it's there.

Do you have a flush valve installed? Make sure that is closed if you do.

Opus · Jul 19, 2019

C-Reefer said:
What is the purpose of a flow restrictor? Obviously to restrict the flow but does it restrict flow coming out of the waste line to raise water pressure? Or something along those lines?

That is correct. It restricts the flow going out the waste line which forces it thru the RO membrane.

Here is a link to the spectrapure 90gpd restrictor

SpectraPure 90gpd Flow Restrictor (yellow) | Premium Aquatics

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