Tank overflow while in city mode

While hooked up through a 50 psi pressure reducer and in city position I am getting a slow overflow from the tank fill spout on the passenger side.  This seems new.  The tank if full but not over flowing, I guess due to the slow outflow.  Switching to Normal mode did not seem to fix it.  When I turn off the water source the overflow stops.

Any thoughts about the problem.  Is the valve leaking in a bypass mode (is the possible)?
Thoughts on troubleshooting?

Thanks, Ken

Welcome Ken!

As a Simpsons fan, couldn't help noticing the name..



(I know... Ken not Kent... but still)

Sorry I cant help with the valve issue, my old coach does not have one. Old and simple like its owner. 

I had a similar problem and had Phoenix replace the 4way valve which seemed to take care of the problem.  I did contact Anderson Brass the valve manufacturer and they are working on a new design that is intended to be more reliable but is not currently available.  I was told it should be available later in the summer.

This thread provides more information https://forum.phoenixusarv.com/index.php?topic=3087.0

Would Ken's 2014 unit have the current-day 4-way valve system?  If not, maybe his on-board water pump has a build-up of mineral deposits allowing pressurized water get past it in the opposite direction.  If so, I wonder if soaking the pump-portion of the pump (not the motor portion) in CLR will clean it up adequately to stop the reverse-pressure leak.

His on-board water pump might also have a check valve.  It has been 11 years since I had mine in-hand.  I don't recall mine having a check valve.

If you do a general (not Phoenix) search for "fresh water tank overflow" you will gets 100's if not 1,000's of hits.  The answer is either a stuck check valve or a leaking 4-way valve.

I would first try lubing the 4-way valve o-rings or at least pull it and see if the o-rings are all in place.  I think @fandj post has a link to info on that.  If the 4-way valve looks good then it is the check valve.  One post I read says to disconnect the city water hose and then run the pump for a while.  The poster states this can reseat the check valve.  Sounds like a long shot to me but worth a try.

One post I read says to disconnect the city water hose and then run the pump for a while.  The poster states this can reseat the check valve.  Sounds like a long shot to me but worth a try.

Jatrax has a good idea, makes sense, surely worth a try.