home built RO plumbing

[Wanabe1972]

I finally got all the parts for my RO build but have a question about plumbing the membrane. I have included pictures. What I need to know is sap in, concentrate out and permeate out. Both end caps are the same so I'm pretty sure one gets plugged. Also I have a needle valve for the concentrate to adjust flow but do you need one for the permeate side or do I adjust pump pressure to match the membrane?83478348.

[Flat Lander Sugaring]

http://mapletrader.com/community/showthread.php?19021-Home-Made-RO-by-TR-Industries

[TunbridgeDave]

The needle valve is for the concentrate side. The permeate comes out freely. I adjust mine to 200psi at the start and by the end of the day it's usually up to around 300, then I wash. That's for my system though with xle's that run better at lower pressure. The center holes are for the permeate so yes, one of them gets plugged. The other holes are for the sap. One end is the input and that end is where the seal (often called the brine seal) is on the membrane itself. That seal directs the sap through the membrane instead of down the space between it and the vessel wall. There is no seal on the other end. The concentrate then comes out the other end.

http://img.photobucket.com/albums/v297/floatinforeva/ROMembrane.jpg

[bowhunter]

You don't want any restriction in the permeate side. The pressure difference between the concentrate side and permeate side is what drives the clean water through the membrane and out the permeate side. The needle valve goes on the concentrate flow out of the housing and is used to build pressure on the membrane. The pressure you have to run will depend on a lot of things, but can't exceed the pressure rating of the membrane, housing and the design pressure for the pump. You need a pressure gauge before the needle valve. It can be between the pump and the membrane housing or after the membrane housing but before the needle valve. There will be a little pressure drop across the membrane so it may be better to put it before the membrane housing and I believe that's how the commercial units are set up.

[stoweski]

So why would some people put a flow meter (non adjustable) on the permeate side if all that it is used for is to read the pressure? Besides curiosity I can't see any other reason to have it.

[jmayerl]

Benchmark flow rates to determine %
Of h2o removal and membrane fouling.

[Wanabe1972]

I think I have it now the pinch of the needle valve on the concentrate side will determine the pressure in the system. The picture from Tunbridgedave helps to make sense of it. I will have to look up the specs on the membrane again. A buddy from work helped pick. The membrane as he does the service on our ROs at work. He picked out a low fowling. Ultra low pressure membrane. Thanks for all the advice and I'm sure ill need more in the coming weeks.