Water coming out of overflow when hooked up to city water.

[JimDarla]

I noticed that our fresh water tank went to 100 percent full when hooked up to city water to the point that some water was coming out of tank vent. Why is that? Thanks.

[Eric.]

Good morning,

The water pump has a bad check valve and the city water is back feeding to overflow your water tank.

Have a good day

Eric

[SuperTrouper]

Originally Posted by Eric.

Good morning,

The water pump has a bad check valve and the city water is back feeding to overflow your water tank.

Have a good day

Eric

X2 - Brad

[Vantair]

Exact same thing happened to us. But we have a recently updated water pump.

Waking up one morning and the awning side was muddy soaked with water leaking out of the fresh water fill.

To solve, we simply turned off the city water connection (to not conflict with cycling the water pump a few times) and allowed the pump to cycle and do its normal thing.

Must have been either simple sediment or a funky position that the check valve semi stuck partially open.

Cycling the pump solved the issue….at least for us.

[uraljohn]

Originally Posted by JimDarla

I noticed that our fresh water tank went to 100 percent full when hooked up to city water to the point that some water was coming out of tank vent. Why is that? Thanks.

Had this same experience on our 2019 FC 25 RBT. Turned off the city water and ran on the pump until fresh water tank was empty. Hoping that through normal use of water turning the pump on and off many times over a day would clear the check valve. No dice. Replaced the pump with exact same model (easy 1/2 hour job) then install a positive shutoff valve to isolate pump when on city water (another 1/2 hour easy job). Now there is no way fresh water tank can fill when connected to city water. Yes, I have to reach in to flip valve to use onboard water but I am OK with that.

[SYC2Vette]

Happened once to us and as others noted shutting off city water then running on pump then back to city water cleared the check valve.

[Hans627]

Originally Posted by SYC2Vette

Happened once to us and as others noted shutting off city water then running on pump then back to city water cleared the check valve.

Pretty much the same here. It was an isolated problem that cleared itself. Must have been some debris in the check valve. I turned off the city water and used the onboard supply. In fact this is what I usually do. This tends to keeps the water fresher in the tank.

[WHUDS22]

The check valve can get stuck sometimes, happend to us, turned off city, ran pump for showers everything till empty, turned on city, kept eye on fresh tank, some suggest turning off on city couple time running water, using hot water too, what ever it started to work again no more problem. Its quite common if you google it.

[Belegedhel]

It doesn't take much grit and crud in a water pump for it to allow water to flow back into the tank. So first, make sure you have a filter between your water tank and the pump, and that you have emptied and flushed that filter. After that, as described above, just cycling some good clean water through the pump may be all that is needed to correct the issue.

good luck!

[JimDarla]

Thank you for your responses everyone.

[uraljohn]

After replacing our water pump due to check valve failure I disassembled the old pump. No crud, no grit, clean as a whistle inside. Still can not figure out why the old pump let the fresh water tank fill when connected to city water.

[Hans627]

Originally Posted by Belegedhel

It doesn't take much grit and crud in a water pump for it to allow water to flow back into the tank. So first, make sure you have a filter between your water tank and the pump, and that you have emptied and flushed that filter. After that, as described above, just cycling some good clean water through the pump may be all that is needed to correct the issue.

good luck!

Good point about the in-line filter. I was lackadaisical about using a filter but after I had the seal on the pump leak I began using one. I have not had the problem since.

It seems as though this has also helped with the pump coming on occasionally because of pressure reduction caused by a leaking internal seal in the pump.

Point being, I now use an in-line filter as it seems to do what it is supposed to do, keep dirt out of the system.