Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. Today he discusses an RV’s fresh water tank
Fresh water tank overfills on city water hookup
I have a 2020 Fox Mountain from Northwood. Strangest thing – When hooked up to city water in the summer I sometimes get water filling up my fresh water tank, to the point where it actually has so much pressure it pushes back out where you put the hose in to fill it up. I actually wouldn’t have noticed if it had not come trickling back out. I have noticed though that it only happens when my outside shower nozzle is hooked up. In this rig the outside shower nozzle is like a compressed air hookup. Any ideas? Thanks so much. —Andrew
It could be one of two things. First, I would check the water pump check valve. On the pump, there is a valve that should allow flow through the pump from the fresh water tank and not allow flow from the city water line. It is common for this valve to get plugged with plastic shavings and other building materials and not allow the valve to close completely. It can also get scaled with lime and sediment from hard water. I would suggest taking the pump out and cleaning all the screens and valves connected to it.
Another issue could be high pressure from your campground source. It’s always good to use a pressure regulator such as this 40 psi inline version. There are some that you can adjust for higher pressure. However, I would not suggest going over 50 psi as the check valve might not be able to handle the higher pressure.
The next place I would look is at the city water/fresh water tank fill valve. Most rigs like yours have a valve that you can turn from city water going through the plumbing system to filling your fresh water tank with pressurized city water without the need to disconnect and use the gravity fill.
If this valve does not thoroughly shut, water will flow to the city water plumbing and the fresh water tank. The only way I know of testing this is to disconnect the water line either at the valve or inline to the tank, hook up the city water, and see if it leaks when the valve is directed to city water or, in this case, “normal flow.” As before, high pressure could cause this to leak, so make sure you use a pressure regulator.
I do not know why this only happens with the shower hose connected. Maybe the shower head has a leak that allows air to vent and high pressure water flows through a check valve. Seems odd, and hopefully someone else has run into this situation and can explain it.
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