City Water Connection is filling my Fresh Water tank to overflowing

[HLB1]

This is a recent development, I keep my freshwater tank drained while traveling. I hooked up a hose to the City Water Connection and it fills the fresh water tank. It overflows from the Fresh Tank fill and that runs constantly. I don't think this is normal but I am relatively new to RV life. Any ideas?

[wrvond]

I'm guessing you don't have a filter on your city water supply line.
The most likely cause is dirt from the city water has lodged in the water pump diaphragm and isn't allowing it to close completely.
First thing to try, since you have water in the tank, it turn off the city supply, turn on the pump and let it run for a bit to see if it clears itself.

[bobbecky]

It's more likely the built-in check valve in the water pump that has debris that is allowing water to go to the fresh tank, or the check valve has just failed doing the same thing. You can do the same things as suggested above, which might clear the debris, or at worse, replace the pump, and if you do, make sure you install a screen device on the suction side of the pump.

[wrvond]

Originally Posted by HLB1

This is a recent development, I keep my freshwater tank drained while traveling. I hooked up a hose to the City Water Connection and it fills the fresh water tank. It overflows from the Fresh Tank fill and that runs constantly. I don't think this is normal but I am relatively new to RV life. Any ideas?

Sorry that didn't work.

It's a safe bet you've got a Shureflo pump but anybody's guess which model.
Here is a link to the manual for the model installed in my Cougar, if it isn't the correct one, you should be able to find it on the Pentair Shurflo website.

Pentair Shurflo 4008 RV pump

Scale buildup on the diaphragm can cause it to leak by. At this point I think you're going to have to open it up and physically inspect the interior for cleanliness. Including that check valve that Bob pointed out.
If, when you turn off city water supply and run the pump, water comes out of the faucet, at least you know the diaphragm isn't torn.

[gearhead]

If you have a KANTLEAK water selector switch in your convenience center that can have a failed O ring and cause similar issues.