I hooked up my black water flush and found water coming from under my cabinet. I removed the inspection cover under my shower and could see water on top of my black tank. Any ideas? —Terrance, 2016 Grand Design 308BHTS
Most 5th wheels have the black water tank in the middle or offset, so the flush valve you actually connect the hose to is not directly connected to the tank. Rather it has a hose going from the connection to the actual spinning valve on the tank. So you have a variety of areas that could leak when connecting pressurized water, either directly behind the service center connection, somewhere along the hose going to the black tank valve, or at the connection of the hose to the valve. This is the connection on a Keystone Raptor 2016 that is mounted on the sidewall but also has the line going to the tank.
Most owners do not think about this flush valve when winterizing and there is often water sitting in the hose from the service center to the tank. When it freezes, the hose ruptures and you have a leak. You should be able to identify if the water is fresh water or black water with a test kit from a home improvement store. My guess is it’s fresh water spraying from a crack in the supply line.