why is water filling holding tank thru city fill?

[gsman36]

I went camping first time in our 2019 premier ultra lite 26brpr and hocked up water to city fill. After about 20+ mins the water is flowing out the overflow for fresh water holding tank. Shut off water and used faucet. Had no pressure, had to use water pump to run water. No switches to be seen. I found water pump but no valves there either. Have not found area to winterize but have one more area under entertainment area for that. An ideas? Enclosed belly so can not track anything.

[opnspaces]

I looked up the manual to your trailer o see if there was anything in there. Unfortunately the manual is onse size fits all and not at all specific.

Keystone manual wrote:
Fresh Water Tank
All Keystone RVs are equipped with a fresh water tank. Tanks vary significantly in size by RV brand & model.
Keystone RV uses 2 different methods to fill the fresh water tank depending on the brand & model.
Gravity Water Fill - Remove the cap, on the exterior connection labeled ”Fresh Water Connection”, and insert the
hose from your water source and turn on the water. While filling the tank, periodically check the monitor panel to
determine the level of water in the tank. When full turn the water source off. If overfilled, water will “spit” back out
of the gravity fill as there is no automatic shutoff. DO NOT leave the RV unattended while filling the fresh water
tank. Overfilling the tank can cause damage to the system components which may not be considered warrantable.
Pressure Water Fill - Hook a potable water supply to the city water fill valve, turn the valves to the tank fill position
and turn on the water supply.

[cavie]

LadyRVer wrote:
Happened to me, just bought a travel home home… 30 minutes later, water all over underneath. Dealer came out.. it was a check valve in water pump, so instead of new pump.. he added a cut off valve just before the pump. Never was right, but it did stop the water from flowing into the fresh water tank.

You should have made him fix the pump AND installed a back flow valve. You can take the pump apart and clean or install a rebuild kit.

[LadyRVer]

Happened to me, just bought a travel home home… 30 minutes later, water all over underneath. Dealer came out.. it was a check valve in water pump, so instead of new pump.. he added a cut off valve just before the pump. Never was right, but it did stop the water from flowing into the fresh water tank.

[CA_Traveler]

The pump or related check valve should prevent backflow from city water through the pump and into the tank.

My pump started allowing backflow. For $10 I added a 1/2" plumbing check valve, adapters and clamps to resolve.

[Old-Biscuit]

IF you do not have a FILL Valve/Position where you connect hose for City Water then water backflowed thru pump internla check valve and filled the fresh water tank

SOmetimes just using the pump will clear any debris that is holding the pump check valve (single diphragm) open and it will close

If you hear pump cycle every once in a while it is probably due to the check valve still leaking (allows system pressure to drop so pump starts builds pressure then pump stops)