Check valve on feed line

[Brent]

Every time I shut down the RO it wants to drain back through the feed line to the stock tank. Gets air in the membranes and when I restart I need to run it on the feed pump to clear the trapped air. Bubbles coming up through the permeate flow gauge and out. I'm thinking this thing needs a check valve just before the feed pump to stop this backward flow. It would save me 5 minutes of sitting and watching bubbles (like watching sap ladders) every time I start.

Anyone else see this ?
Anyone else got a check valve in the system ?

[Gary in NH]

Brent, I have a manual shut-off valve right before the RO pre-filter. I figured the check valve was more thing to have a problem with later if it didn't seat completely. The pressure in my RO will decrease as it sits for a few minutes after shut-down. After I switch over to rinse water and re-pressurize I still see some micro-bubbles through the concentrate flow meter. I think they come out of solution when the pressure is reduced but they clear up within a minute or two of rinsing.

[Amber Gold]

I'm looking into this as well, although primarily for a different reason. I'm going to run a 1.25" to 2" feed line from my tanks to the RO. Last season when the RO would shut down, the RO would drain back into the permeate tank or sap storage tank and would freeze the line. I'd like to avoid this issue this season and install a swing check valve at the pump. Any reason I shouldn't do this? Thanks

[maplwrks]

Josh---I would not put a check valve in the feed line. I would just throw a guillotine valve in before your feed pump. I have bubbles going through my RO every time I start up. Anytime you run your RO dry, you will get air intrduced to your machine.

[Amber Gold]

Mike, I'm not concerned about the bubbles, but concerned about backflow out of the RO room. Last season when I knew the tank was getting empty, I'd sit at the RO and when it shut off, I'd immediately close the valve. This worked well except for when I'd forget or when I'd rinse the membranes w/ permeate the next morning, the line would be frozen. I'm also not in the SH when things are boiling and this is an issue.

[Thad Blaisdell]

Make sure the end of the pipe feeding the tank is above the fluid level. That way it cant run back to the RO. Next when done RO'ing concentrate, chase it up with permeate, then let it drain back to the RO and stop the fluid once it is in the room.

[Amber Gold]

The outlet to both of the tank's is higher than the feed pump, but the RO machine is higher so there's enough head to push the sap/water back into the tanks. I shut it off now by hand when the RO shuts down due to lack of fluid, just looking to have it done automatically, but not create a problem by doing so.