RO/DI auto shutoff troubleshooting

[markus902]

Hi Folks,

I have been running my SpectraPure 4-stage RO/DI for a while with an auto shutoff valve for a while now. It was working well for a year but I recently had to move the system. I tripple-checked that I have plumbed in the shutoff valve correctly (see scheme below), but no matter what I tried it does not seem to activate. When I shut off the manual valve at the end, water keeps flowing out the waste water line. The system is running on a booster pump (60 psi), so low input pressure should not be the issue. Has anybody an idea why this is not working?

2 suspicions I have:

1. Defective Membrane
2. Bubble In the 4th stage that I can't get out

Faucet --> High Pressure In ASOV --> High Pressure Out ASOV --> 2 First stages --> Membrane --> RO Water out --> 4th stage --> Check valve --> Low Pressure In ASOV --> Low Pressure Out ASOV --> Manual Shutoff valve to tank

Thanks in advance!

 

[Reefing Madness]

 

[StickyThwomp]

Definitely not an expert, but I just troubleshooted the same thing in my setup.

Replaced the asov and it appeared to fix it. Came back again later and then appeared to be due to high input pressure and not enough flow limitation on the concentrate line (mines adjustable, and I had it at 4:1, but that didn't seem enough with two RO membranes?). Working fine now as far as I can tell.

That said, a busted asov or missing check valve after the permeate output seem to be the more common causes.

 

[theMeat]

It takes a minute or few for the asov to shut

 

[markus902]

Sorry for the late reply, I kinda forgot I had this post going. Here’s where I’m at: I took out all the filters and the membrane, replaced the ASOV and tried the setup. Everything works fine this way. Now I put in all new filters and a new membrane, same issue. I lowered the pump pressure from 80 to 60 psi, no change. It looks like the post membrane pressure is too low for the pressure switch and the valve. I’m going to get a pressure gauge coming weekend to see what the pressure situation behind the membrane is when I shut off the valve.

It takes a minute or few for the asov to shut

Interesting, I’ve let it run for quite a while after shutting the valve and it didn’t work why would it need such a long time to build up the pressure?

I’ll post an update once I measured.

 

[theMeat]

Yeah, guess it needs to build pressure hi on one side, low on the other for the valve to shut. Can sometimes hear them make noise until they shut.
What size membrane, what size flow restrictor?

 

[markus902]

Ok, it’s fixed. I just let it run for a while and about a minute after shutting off the pressure switch and ASOV activated (was too impatient the first couple times). Now after trying a few more time, the time lag is getting shorter. It looks like as air gets purged out of the system it gets better … air acting as a cushion for pressure buildup. Looks like the old ASOV was bad, which is why I got into this situation in the first place.

It’s a 75 gal/d membrane with a 420 cc flow restrictor.

 

[Buckeye Hydro]

1. Realize that a high pressure ASOV is plumbed differently than a standard ASOV.
2. If you have air trapped inside your DI stage you'll have to wait for that bubble to be compressed before the ASOV works. Suggest you burb that trapped air out.