Originally Posted by Old
See pic. Water coming from here when gray tank full. Anyone know why. 2014 Flagstaff.
Is that a ceiling vent? The only gray tank plumbing above the floor level would be the air vent pipe but that goes through to the roof. I'd think the water would be backing up into the sink or shower before you filled the vent pipe, unless the sinks AND the shower use a HepvO membrane valve instead of a traditional P-trap.