Low RO output

[MEP001]

I decided to read the directions, and it recommended a psi of no more than 150 and use of cold water. This will slow the fouling by not push water as hard against the pours, and the warm water would make the pours expand. Neither of which sounds good.

I assume you're referring to the membrane that recommends that?

I've always worked with Dow TFC membranes, always set them up at 200 PSI whenever possible, and usually make sure to have a high flow through them to prevent fouling. It's not unusual for them to last 10 years under those conditions.

 

[RAATCB]

I was told that maybe my "flow control valve" might be clogged and that's why I'm getting very little reject. Also another person said pretty sure the pump is going out because it cannot push all that volume out and that's way reject is flowing so low. I understand what
you're saying MEP001 but this system was not made by someone in their garage, it's an RO company that put and engineered all of it.

 

[MEP001]

Someone may have replaced the original pump with what's on there now.

The pump may be going out, but it's also too small. Even at peak output you can barely get a 1:1 product/reject with no internal recirculation. That's not enough to maximize the life of the membranes.

FWIW, I've also engineered RO systems and re-engineered about 100 others.

 

[Jeff_L]

I was told that maybe my "flow control valve" might be clogged and that's why I'm getting very little reject. Also another person said pretty sure the pump is going out because it cannot push all that volume out and that's way reject is flowing so low...

You can always take apart the components to look for buildup. Especially in the ends of your vessel that holds the membrane. I also feel the pro on is too small, especially for two membranes. How many cubic feet is your carbon filter? Rule of thumb is 1 cubic foot per membrane.

 

[RAATCB]

I have about 1 cubic feet of carbon. It was just re-bedded when I replaced membranes. The flow control is threaded with pipe dope to a manifold that's cpvc/plastic block. Only worry is about rethreading it back on manifold, if it cracks there are no replacement manifolds to buy. That's why I'm hesitant about removing it.

 

[MEP001]

If someone told you the flow control valve on the carbon filter head is clogged and causing low reject, they have no clue. You wouldn't have any inlet pressure to the system and the Procon would be whining like mad because it's starved for water.

 

[RAATCB]

If someone told you the flow control valve on the carbon filter head is clogged and causing low reject, they have no clue. You wouldn't have any inlet pressure to the system and the Procon would be whining like mad because it's starved for water.

Flow control valve built into my RO system. The reject line has a flow control valve that will drain 2.5 gpm. Maybe that flow control valve is clogged.

 

[MEP001]

How does the system regulate pressure? A lot of them just have valves that control flow to the drain and nothing else. If it has a regulator, is it a bypass type? Where does that bypass to?

 

[RAATCB]

We use a paraplate regulator to increase/decrease pump pressure. One line out of the regulator gets tee'd back for recirculation before I believe it gets rejected. I've seen on other systems they use needle valves to increase/decrease drain flow. Mine is fixed @2.5gpm. The flow control valve looks like this

http://www.deanbennett.com/dole-flow-control-valves.htm

 

[MEP001]

It sounds like you have multiple problems.

That valve says it's only accurate up to 125 PSI, so I don't see why it's used in this application.

The regulator may also be in the wrong application - what model is it? You can test if it's bad by pinching off the bypass line, and if the pressure doesn't increase the regulator is at its limit. It sounds like it's working as it should though.

If the regulator is on the output of the pump, you're probably not recirculating any concentrate flow, and you should be rejecting at least 2:1.

I can understand if you want to just replace the whole thing, but it'll cost at least $5000 when you can fix it with maybe $500 in a pump and some brass. You'll learn a lot about how it works in the process.