I have a DuPure Impression water softener that worked fine up until recently when I noticed the brine tank was always full of water. Extensive debug has shown me that during the brine draw phase that water is actually flowing into the tank. I have removed all of the equipment in the brine tank and just have the hose going into the full tank of water. I can see that water has very good pressure during the brine fill stage. During the brine draw stage, it is much less but still a pretty decent flow.

I'm not really sure how to check for leaks. I sprayed soapy water all over the control valve and don't see it drawing in anywhere. I took the brine elbow assembly apart on top of the control valve and everything looks ok.

DuPure wants $200 to come inspect this but I know it has to be something simple.

Maybe at a minimum someone could explain how the water gets drawn from the brine tank into the resin tank. There are no pumps or anything, so what creates the suction? I've tried googling without progress.

Thanks in advance!