RO/DI shut off valve, how is it supposed to work?


New member
I guess 1 side gets back pressure, the other side is supposed to close?

I installed it, 1 side is on the output, the other side is on the line from filters to membrane.

but its not stopping... obviously I seal the output, but the waste line continues to flow. what gives? is it backwards or what?


New member
It usually takes a minute or two to close, and when you drain the system it may not function until the air is removed which may take a while. Just close the output and let it run for a while. Also, I don't remember if they're directional or not, but check for any arrows or directions on the valve.


New member
It definitely takes a while to close from back pressure.
Mine takes a good 10-20 minutes till you don't hear any waste water flowing.

Never timed it but just watching it I would never hear it stop.
But coming back a half hour or hour later and everything was fine.

Here's my setup:

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New member
ah, I didnt give it much in the way of time. there are some air bubbles in the DI container also.