Small Scale RO Issue

[Blacksheep7]

Hello everyone.

Hopefully you all can help me out and point me in the right direction on the problem I am having. I thought I was able to get everything together on my RO build, but am having some problems. I connected all the tubing per instructions and pictures I have seen in many places. Once the pump started, I am only getting water out of the permeate line. No matter how much I turn the relief valve on the concentrate line I get nothing and also no pressure building. Do I have an air leak somewhere? I do have a small water leak that I will be taking care of and also one of my housings had a small hairline crack, so I will have to get a new one. I even went down to just one membrane and still cannot get it to work. I am glad I tried this a month ahead of time to get the bugs worked out.

Specs:
Aquatech 8800 pump
10" filter housing and filters
3 - 400 gpd RO membranes (only 2 for now)
3/8" inlet line to the pump
1/4" lines throughout the rest

Just not sure what I am doing wrong.

Thank you,
Jason

[TreeTapper2]

I'm guessing you have the concentrate and permeate lines mixed up. Put the valve on the line you are currently calling the permeate and see what happens when you close it.

[maple flats]

Are you pumping the sap into the outer part of the housing, with a hose to both the inner section of the membrane and the outer but at the opposite end? Then the needle valve should restrict the flow out the outer hose, creating pressure to push water thru the membrane. The pressure gauge should be just before the needle valve and after the needle valve a hose should transport the concentrate. If it is all connected like that, you do have a problem someplace. Are you sure the seals are good on the membrane?

[Blacksheep7]

Thank you for the replies. I assumed as well that the lines were switched. I placed the valve on the opposite line and then was able to create some pressure and also get water out the other line. The strange part is I have my valve now on the right outlet port of the housing and by all the pictures I have seen it should be the left. The left looks like it is the straight through, but I do not seem to get anything from that port. I have it set up to run in series. Bottom left into the top of the next. Bottom right was connected to the other bottom right thinking that is permeate. I have switched the lines so many times now trying things, I am just about ready to quit for the evening. I think I need to regroup and look at it again. Also look at many more examples.

Jason

1741117412

[Blacksheep7]

Wow. Just looked at a couple more pictures and videos and my RO housing bottom ports are reversed from all the others that I watched. I cannot believe I did not see that before. Always something easy. Thank again for the help.

Jason

[maple flats]

To know for sure, open the pressure canister and remove the membrane. Then look in, the feed should be into the outer portion of the canister and out the other end also out the outer portion. In that line is where the pressure controlling needle valve should be, that will be the concentrate. Then at either end, the permeate will come out the center port. In use, the high pressure pushes sap into and all around the outside of the membrane and as you adjust the pressure upward, that back pressure forces permeate thru the membrane to the center of the membrane, while the sugars will not pass thru, so they continue on thru the outer portion of the canister and out the other end.

[bowhunter]

Dave's dead on. For all of those out there building your own RO, one word of caution. If you accidentally put pressure on the permeate side of the membrane you can do permanent mechanical damage to the membrane, so be very careful about the hook up. The one way you can do this is to hook up the sap in off the pump into the permeate out connection.

[Blacksheep7]

Thanks again guys. I finally noticed it when I did look in the inside of the canister. You can see from the picture that I posted above that what you stated is correct. I just hope now that I did not damage the membranes by having it hooked up incorrectly. I did not have it that way long, so I guess we will see.

Thanks again for all the input and help! I really cannot wait to put this thing to work in a month.

Jason