Disappointed in my homemade RO and need advice

[DRoseum]

I run two 400 gpd membranes on the aquatec 8852 pump at 100 psi without a problem.

Should have been more specific. My first 2 membranes are in parallel. I agree that you should be able to get this working.

[GoldyCon]

I can stop the flow of concentrate but when I do that the permeate is also reduced. For some reason I seem to get the best volume flow of the permeate when I run a 25/75 split. If I go higher than that the volume decreases from a weak stream to a steady fast drip.

The 50/50 split works for a bit but within 10 mins they are no longer matching and the permeate is back to a drip. At this point I usually open the needle valve all the way to try and flush the system out which seems to help.

[DRoseum]

Are you able to post a picture of the plumbing coming out of the membranes?

[30AcreWoods]

Something isn't adding up here...

This is a long shot and I'm virtually certain isn't the issue, but have you tried to move up to a 3/8" line where the two 1/4" permeate lines come off the bottom of the membranes? Use a 1/4"x1/4" x 3/8" wye.

Also, not all needle valves are created equal, I've learned. Some of them leak a bit at the valve assembly. Do you hear any hissing around the needle valve when it is cranked down to 50/50?

[carls47807]

Pull your two permeate outlets and measure their flow independently. Even at 100psi you should be running better than you are. At this point I would suspect your membranes are bad. Use 30acres suggestion and go to a 3/8” line as well.


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[GoldyCon]

Update

Things are running quite a bit smoother now after 2 days of use. Initially I was recirculating my concentrate but I found that running fresh sap in one pass was giving me 4% con and a much better permeate flow. Additionally, I also found out that my helper used a small amount of olive oil to lube the filter when putting it in the membrane. I’m guessing this oil caused some of the issues but is now flushed out. It also makes sense why I’m seeing improvements over time.

[30AcreWoods]

You might want to try an acid wash and then a soap wash/rinse. I bet you will see some really great improvements.

[MapleCamp]

I use the same pump with 4, 150 gpd membranes in series , I get up to 140 psi on freshly cleaned membranes , and 8% concentrate . I would think you should get better than 4%. I have .25 inch tubing on every thing. Check your prefilter I change after every run which might be 2-300 gallons. Try cleaning as described elsewhere on maple trader I bet it will help. My sap averages 2.2%