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So, How do I work this thing? (reverse osmosis unit)

Big Chris

Big Chris

Member
After much head scratching, changing some plumbing & new membranes I finally have my RO unit working.
Turns out the previous owner had it plumbed incorrectly. He had the product water from membrane #1 flowing into membrane #2's core (where product water exits) and water from membrane #3's core flowing to the reject valve. Basically I'd try to turn on the system and the pump would stall, and trip the breaker inside the control cabinet.

If you remember, this unit is from this THREAD
So looking at the picture below where do I set this?
I have a procon 116N480F11XX pump than can produce 250psi
My membranes are THESE. Which are rated for 225psi, but "optimum pressure" is 100psi.
So where do I set my Reject?
Where do I set my Recirc?
Am I setting the control valve until I get to 100psi?
What happens if I set it to 150 psi?
What do I do with the Recirc control valve?

IMG_2972.jpg
 
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Your membrane is spec'ed at 225 psi (not 100 psi). Should produce 2400 gpd, or 1.6 gpm (per membrane) given factory spec conditions. 3 x 1.6 = 4.8 gpm, Given that your tap water temperature is likely less than 77F, your permeate flow looks decent. Min concentrate flow should be 3 gpm.

You should crank your pump pressure up if you can.

I would not have recommended that model membrane for you.
 
I took a gamble on cheap Chinese membranes to see if I could get the unit working correctly. It was a hard sell to buy expensive membranes when I couldn't get the unit to run. It would just stall the motor/procon pump. It wasn't unit I drew the system out that I realized what the issue was. And quite frankly all I ever did was reassemble the thing the way I took it apart. Once I realized what the issue was, I can see how someone could reassemble it incorrectly.

In the bottom right, you can see that city water temp is about 50° F, it will max out late July/early August at about 65°F and will bottom out to about 35°F in late Jan.

So I should up pressure and try to get close to 225psi/4.8gppm while keeping reject flow at 3gpm?
What do I do with recirc?

Here's a short VIDEO


IMG_2975.jpg
 
So I should up pressure and try to get close to 225psi/4.8gppm while keeping reject flow at 3gpm?
Yes.

I can't advise you on the recycle issue unless you can give me the results of a lab analysis of the water. But, if it is city water, and you have appropriate pretreatment - meaning the feedwater is dechlorinated and soft (or softened) - I'd set the recycle at one half of the concentrate (1.5 gpm).
 
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Nice! I'd turn that recycle up to 3 and recycle down to 1.5.

Is there a globe valve right after the pump or some other valve where you can increase the pump pressure? If not, you don't have enough pump to crank out the 225 spec pressure. When you're ready for new membranes we can look at membranes spec'ed at 80, 100, or 150 psi.
 
Thanks!
The pump is a 116N480F11XX, so it's supposed to flow 480gph. So that should do 8gpm. It doesn't have a pressure regulator on the pump.
I can turn the control valve and get more pressure, but I'm wondering at what point do I overload the motor and trip the breaker?
At some point I may consider adding a 4th pressure vessel and membrane.
 
But the pump output isn't at the pressure you need. The pump should be fine once you get membranes installed that are a better fit for the system.

Don't close off the concentrate in order to get more pressure. Leave the concentrate at no less than 3 gpm.

Can you send some pics of your pump?
 
OK I'll leave concentrate (reject) at 3gpm.
These are what I had on my phone, I can get you some better pics later this afternoon.
I currently have "recirc" set to 1.8 gpm, if I lower that, pressure goes up. I see you recommended setting it to 1.5gpm. I'll see what that does and report back.


IMG_1452.jpgIMG_1456.jpg
 
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