Aquatech 8800 on RO - Low pressure problem

[climb.on]

I built an RO system with an aquatech 8800 pressure pump. Ran it for the first time last night (with just water) and I can't get the pressure over about 50 PSI. The adjustment screw has almost no effect on pressure while running well water through it. Maybe 5psi. I've screwed it all the way in and even removed it. Bad pump? Problem with my setup?

This is VERY frustrating as I hoped to run my first batch of sap through it today.

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[climb.on]

Here are a few more pics:

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[climb.on]

Are my membranes in backward?

[SDdave]

First thing is to make sure the set screw is put back in. Then get the pump going to about that 40 to 50 PSI range. When you got that turn off/close the concentrate needle valve. This is the way to make back pressure on the system. But watch it closely, the PSI will shoot up rapidly. I usually go to 130 PSI and then open the valve to get around a 120 PSI while its working. When you run sap through it you'll have to play with the needle valve to get your desired results, i.e. outflow ratios of permeate and concentrate, sugar %, what nots.

That should get you up and running.

SDdave

[SDdave]

My bad, should be about 20 to 30 PSI when it's wide open. That's what mine is running at right now.

[climb.on]

Thanks SDave. That helped, but the most I can get out of it with the needle valve closed is 95 psi.

[climb.on]

My bad, should be about 20 to 30 PSI when it's wide open. That's what mine is running at right now.

Oh i didn't see this other post. So you get 130psi with the valve closed, 120psi when it's working and 20-30 when it the valve is wide open?

I am getting 95-100psi valve closed, 80-90 with a 2:1 flow rate, 40-50psi when wide open.

Should note this is well water and it's about 32 degrees out.

[SDdave]

Yes.

Now that your getting your 80 to 90 play with that set screw. Looking at it you might want to create some more back pressure on that needle valve. Which will decrease your concentrate outflow. I've never had the patience to measure out the ratio on the flow rate so I can't be much help on what you need on that. I've always shot for 120 to 125 PSI and then ran a sap hydrometer on it to test the results.

Gotta man a booth at a trade show, but I'll check in later to see if you got it. I think you will in a matter of time.

SDdave

[climb.on]

I started a batch of sap and the pressures seem correct now. With 50 degree sap, needle valve closed, I was able to adjust the pump to 125psi and it dropped to about 120 psi when I opened the needle valve a little. I started getting about 6% concentrate out, but I am also seeing 1% sugar in the permeate. I've tried tweaking the needle valve open and closed a bit, but I can't seem to eliminate the sugar in my permeate. Any ideas there?

[hodorskib]

Your setup looks very nice and from the pics seems to be hooked up correctly. One way you can test to see if you have a faulty/failing membrane is to use one at a time for about 10-15 minutes. Measure the sugar in both concentrate and permeate lines and see which one is passing sugar. Not sure how you are measuring sugar % with a hydrometer or refractometer but you may want to make sure whichever one is calibrated correctly. I had purchased a cheap refractometer several years ago and this year it is giving me false reading no matter how many times I recalibrate it.

[climb.on]

Your setup looks very nice and from the pics seems to be hooked up correctly. One way you can test to see if you have a faulty/failing membrane is to use one at a time for about 10-15 minutes. Measure the sugar in both concentrate and permeate lines and see which one is passing sugar. Not sure how you are measuring sugar % with a hydrometer or refractometer but you may want to make sure whichever one is calibrated correctly. I had purchased a cheap refractometer several years ago and this year it is giving me false reading no matter how many times I recalibrate it.

Thanks hodorskib. I really appreciate you chiming in. I'm testing with a $15 hydrometer. I believe the pressure issue I had is no longer an issue. No sure what corrected it, but I am able to adjust the pump at the set screw and get 125psi with the needle valve closed. With the valve open running 1:3 or 1:2 it drops to 120psi. With either ratio I get 1%-1.5% sugar in my permeate. I dropped the pressure to under 100psi and still get about the same sugar in the permeate.

I just started running the permeate again and my concentrate dropped to about 3% and am still getting 1% in my permeate. My head is spinning and I'm ready to throw this **** thing in the trash it's so frustrating. Bad pump? Bad Membrane? Bad pressure gauge? Bad hydrometer? Dumb operator?

Part of my frustration is that I still just can't understand how these membranes even work. So if I close the needle valve all the way and I have all the liquid running out the permeate line, logic tells me that the % sugar coming out should match the liquid going in. But how would it then go to zero when I crack the needle valve on the concentrate line. I keep htinking I have this hooked up wrong, but I've checked 100 times and I don't think it is. Maddening.

[Clinkis]

Have you checked your hydrometer with tap water to see what it reads? Also you can take the permeate from each individual membrane. I would start there and see if one is bad. It kinda sounds like your hydrometer might be leading you astray. When I used to use this same RO I ran mine about 50:50 and it never passed any sugar. I only every brought it up to 6-7%.

Just remembered something else.....I know this sounds a little obvious but make sure your hydrometer isn't resting on the bottom of your cup when you are reading your permeate. If my cup isn't completely full it will show 1% sugar because hydrometer is bottomed out. Made this mistake myself. When you are taking your reading push down on hydrometer and make sure it moves.

[climb.on]

Have you checked your hydrometer with tap water to see what it reads? Also you can take the permeate from each individual membrane. I would start there and see if one is bad. It kinda sounds like your hydrometer might be leading you astray. When I used to use this same RO I ran mine about 50:50 and it never passed any sugar. I only every brought it up to 6-7%.

Just remembered something else.....I know this sounds a little obvious but make sure your hydrometer isn't resting on the bottom of your cup when you are reading your permeate. If my cup isn't completely full it will show 1% sugar because hydrometer is bottomed out. Made this mistake myself. When you are taking your reading push down on hydrometer and make sure it moves.

Great suggestions. Thank you. Just tested the my tap water. Reads 0%. At least I can eliminate that component. Also not resting on the bottom of the cup.

I guess I need to start testing one membrane at a time.

[climb.on]

Membrane #2 = BAD!! I did what you guys suggested. Ran the system one membrane at a time and got 0% in 3 of the 4. I could tell almost immediately that #2 didn't run like #1 (and the 3 & 4). It had a much higher flow rate and the pressure dropped off a bit. I've got it hooked back up and running on 3 membranes.

It there a way to fix the membrane? Could it be the housing?

[hodorskib]

There is no way to fix the membrane but if you are questioning the housing put it in a different one and test. My first year I ran 3 membranes and it will work to about 6.5% so that is still a huge time and fuel cost savings. If you ordered your membranes from Amazon.com return it and when the new one arrives you can leave it in the package for next year. The membranes look like a roll of paper towels and the pressure pushes the sap through the layers. Only water molecules can pass through them and everything else gets discharged (especially sugar). Hope this helps.