RO with no permeate?

[wildlifewarrior]

So I got my homemade RO system hooked up and turned on. I thought I was in buisness.... Nope I am sitting here boiling wondering what I did wrong. I have them run in series aquatic 8800 pump, 12 inch membranes and no water commin out. Any ideas?
Thanks
Mike

[maple flats]

check your pressure. Are you saying, sap is going in, but no permeate out? Did you plumb it with the high pressure entering the outer space in the membrane vessel and permeate exiting thru the center? Do you have a restriction valve on outflow of the concentrate to get pressure on the membrane to force the permeate to pass to the inner core to exit with no restriction?

[wildlifewarrior]

Hi Flatts,
I had the whole rig up and running, just like the pics in the other homemade RO threads, Line going from the filter to the first membrane, then that concentrate going to the second membrane through the inlet on the top. I put the membranes in the only way that they would fit, or I thought they would fit. The sap was going out as fast as it was being pumped in. I put my thumb over the outlet to try and increase the pressure and nothing, just some strain on the pump. So you think I probably have the membranes in backwards? I will see about getting a restriction valve put on too.
Thanks for the advice I will post again when I figure this thing out or if I get stuck again,
Mike

[SDdave]

Wildlifewarrior,

Do you have it plumbed correctly? I thought I had it perfect when I did my pre-run and flushing runs, only to find out that I didn't. The permeate line is the one off to the side, with the water line being the more centered outlet. As for the membranes, if you have the Dow filmtech 150 GPD filters the rubber bushings go down inside the tube. Also do you have the needle valve plumbed on? When the needle valve is totally open the sap will exit as fast as it comes in. Hope this all helps and what not.

SDdave

[maple flats]

At the top of each of the membranes there is a seal that when you study it, each is a u shape. To seal the U opening must face the direction on flow, thus if the sap enters the bottom of the 1st membrane, the seal on that one should be open facing down, then if the loop takes the pressurized flow in the top of the second membrane, that U should face up. If these are facing the wrong way you don't get a seal against the outer vessel. When I swapped out membranes, I found that they were shipped from the factory facing the same way, I had to pull one out and reverse it. To determine this, remove the membranes and carefully remove the black rubber (neoprene?) seal and determine which way the open U faces and the insert so each can seal. These seals work when the infeed pressure fills the U shape pushing it tight against the membrane and the canister.

[Clinkis]

I noticed you said you were going to ad add a restricter valve? I assume you mean a needle valve? If you don't already have a needle valve to create the min 100lbs of back pressure you will get no permeate. Add your needle valve and put a pressure gauge on it and get the pressure on the membranes up to at least 100lbs.

[maple flats]

Clinkis is right. Without a restrictor valve the sap will just take the easy path and no water will be forced thru the membrane, sap will just go in one end and exit the other with either zero or at best extremely little water crossing thru the membranes. My RO seems to work best at 275 PSI, but it I running a second pass I lower it to about 250. Depending on the membrane housing and the clamp closures used, you may not want to try for that high, but you need some pressure and resistance on the sap at membrane exit for permeate to be removed.
My RO is limited to 300 PSI max, the much more expensive one go up far higher than mine, to achieve even higher concentration in 1 pass, I need to do 2-3 passes. At 1 I get between 6-8%, a second raises that up to about 12% and a 3rd can get to 15%. That is the highest mine will do, or it plugs and I need to run a cleaning cycle.

[maplwrks]

Do you have a plug in the center of the membrane?
You should plug the center hole on the bottom of the membrane to force the sap through the membrane.

[Clinkis]

Clinkis is right. Without a restrictor valve the sap will just take the easy path and no water will be forced thru the membrane, sap will just go in one end and exit the other with either zero or at best extremely little water crossing thru the membranes. My RO seems to work best at 275 PSI, but it I running a second pass I lower it to about 250. Depending on the membrane housing and the clamp closures used, you may not want to try for that high, but you need some pressure and resistance on the sap at membrane exit for permeate to be removed.
My RO is limited to 300 PSI max, the much more expensive one go up far higher than mine, to achieve even higher concentration in 1 pass, I need to do 2-3 passes. At 1 I get between 6-8%, a second raises that up to about 12% and a 3rd can get to 15%. That is the highest mine will do, or it plugs and I need to run a cleaning cycle.

With these types of membranes and pumps the max pressure is about 125psi.

[maple flats]

OK, then run it at 100-120 max PSI.

[wildlifewarrior]

Hi Everyone,
I put the needle valve in and sure enough…permeate a flowing! I appreciate the help guys! I ran it for about 12 hours and removed about 40 gallons of water which I was wicked pleased with. Thanks again for the help this got me so excited for next season, to bad the season here is basically over.
Mike