Need help with RO solenoid shut-off

[Delphinus]

In retrospect, I don't have 20 gpd of evaporation, it's more like 10gpd peak, and I'm not sure if I have a 50gpd membrance or a 24 gpd membrane. But still I guess that's almost 50% or 25% (depending on membrane) of capacity so I guess it still works as an explanation. Even on for 25% of the time makes sense, that you'd hear the unit going pretty often. Just a real eye-opener on the amount of evaporation this really is, I suppose.

I also maybe lied a little about all the downstream tubing being pex. I have the line T-d off to a 30g rubbermaid so I can have 30g of RO available at any given moment. The tubing that services this bucket is a sort of soft vinyl. It can handle the pressure OK (it used to be an indoor plant watering thing) but the hose is .. how would one describe it ... kind of soft and supple? So maybe it's stretching a bit which causes weird things to happen with the backpressure which in turn makes the solenoid weird? Maybe I should try replacing all my line with pex. I'm just out of pex at the moment.