Dear Dave, In the last two nights of our three week trip, our city water began to enter our fresh water tank and overflow onto the ground. Can you tell us how it happened? — James, Thor’s Castle, 2018
Dear James, this could be one of two problems depending on the design of your plumbing. If you have a city water bypass valve that allows the fresh water tank to be filled with city water pressure when connected, the valve may not close all the time. This valve is a left/right valve that diverts city water from an outside source to the plumbing for all sinks, toilets and showers, or when turned or diverted, diverts water to a fresh water tank to fill before exiting. Without this valve, the owner would have had to fill the reservoir with fresh water by inserting a hose from the water source into the gravity inlet on the side of the rig. When switching to city water, these bypass valves may become loose and not close completely, or their closure may be clogged with calcium or lime.
The second problem could be a weak or clogged backflow fuse on the water pump. When connected to a city water supply, pressurized water bypasses the onboard water pump but has pressure on the back or outlet side of the pump. There is a non-return valve that should only allow water from the pump to pass through. If it is weak or the calcium or lime does not allow it to close, the pressurized water from the city’s water source will be pumped back into the fresh water tank. Check out an article about it here.
Dear Dave & James I have a Berkshire that did the same thing. Dear Dave & James I have a Berkshire that did the same thing. Dear Dave and James, I have a Berkshire that has done the same. Dear Dave and James, I have Berkshire doing the same. I have a valve that I can turn to city water to fill the RV with fresh water and tank water. When using tap water, the valve only turns slightly to fill the tank. It may be 1/8 inch closer to the tank fill. I had some water coming into the fresh tank and that was enough. The fresh water tank fills up and starts to overflow in 1-2 days. I mean, make sure the valve pointer points directly to what you want it to do.
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