Hobby RO Pump Suggestion

[sweet acer]

I just built a 5x400 RO with a new 8900k pump but can only about 30 psi. I adjusted the pressure screw in untill it got extreemly loud but was only able to get 80 psi. The only difference between this build and my previous 3x400 is the size of the hose. i used 3/8 hose for the 5x400. Any suggestions?

[DRoseum]

Are you adjusting the needle valve on your concentrate line to increase pressure?

Some basic things to check that I've seen before
(1) pre filter housing installed in correct flow direction
(2) are all your membrane housing ports correct? Make sure you aren't mixing up which one is permeate amd which one is concentrate.
(3) are you processing sap? Water won't get up to 100 psi

I used 3/8 in my 5 x 500 builds without any problem.

[sweet acer]

Thank you Dave. My 81 year old brain must have been foggy as I now remember the water issue. Checked everthing else and was built correctly. We have had subfreezing weather for at least 10 days so will have to wait a few more days to test it on sap.
Thanks again.

[Mean_Oscar]

Is the same pump going to get sap to a higher ultimate concentration level with a 75 or 150 gpd membrane?

[DRoseum]

The membrane gpd rating indicates how much permeate it is able to remove at a given pressure and flowrate. The 150 gpd membrane will remove more permeate resulting in a slightly higher concentration.

That's said, I think a single 150 gpd membrane on a coronwater typ-8900 pump is really undersized. How much sap do you process at a time? That pump can support up to 5 x 500 gpd in series (2500 gpd total) and process about 40 gallons of sap into 20 gallons of 2x concentrate per hour.

You want to match your pump flowrate at 100 - 120 psi to the capacity of your membranes so that each membranes recovery rate will be in the range of 15 - 20%.

Recovery rate is defined as (permeate outflow) / (inlet flow) for each membrane. The price of a 400 or 500 or 600 gpd membrane isn't that much more than a 150 (naybe 2x as much)....but it removes 3 or 4 times the amount of water per hour.

[Mean_Oscar]

Started with 2 x 75's on an 8800 and now up to 500 on same pump. Nice to get water out faster but can't tell any difference in ultimate (flow gets down to almost nothing / stalls) concentration. Would moving 5 mic housing upstream of pump help? Realize I might need a booster pump then.

[DRoseum]

There are multiple 8800 series pumps, with the 8852 having the highest flowrate. Which do you have?

An 8852 should run a single 500 gpd membrane just fine. What pressure are you running it at?

You don't want to run it so that your concentrate is nearly stopping. That means your recovery rate is really high and that's bad for the membranes. Back off the pressure to increase the concentrate flow rate.

Don't move the filter housing in front of the pump. That will really kill performance.

You could run the 500 and 2 x 75s in series as well, especially with a higher flow pump.

[Mean_Oscar]

The '500' is actually 2 each 100s and 2 each 150s. The pumps are an 8852-2J03-B424 and another the same but B423. My thinking on moving the 5 Micron filter to the intake side of the pump was that like removing a resistor in a series circuit, the voltage drop across everything else goes up. In this case, the pressure should go up. I could stop worrying about the filter housing failing and leaking: a big part of chickening out at 100 psi.