Originally Posted by herk7769
I am attaching a diagram of the water system.
On the city water hose connector outside the camper there is a screen (make sure it is clean) UNDER that screened rubber washer is a one way check valve that prevents water from dumping overboard when you run the pump and don't have a hose hooked up outside.
INSIDE the pump is a one way check valve that prevents city water pressure from flowing THROUGH your pump and filling your fresh water tank when you hook up the hose.
Your pump will not run even if the switch is turned on unless it "sees" water pressure below it's "turn on value." As long as you have water pressure in the exterior water (city) hose HIGHER than the pump's "turn on pressure," the pump will never run.
Oh, PS: When you winterize with RV antifreeze using the inlet on the water pump your MUST either blow air into that city water valve to flush out the water in the check valve or use an adapter to connect your shower wand to the city water inlet and use the shower wand to flush out the check valve.
Forgetting to do this will result in a city water inlet replacement in the spring.
Herk's water system diagram is pretty much correct (I have the same one, from a source that I don't remember now), except that it doesn't show the water heater bypass that is common in most modern RV's.
To make the diagram complete, simply draw in a connecting line between the cold water inlet and the hot water outlet of the water heater, with an open/close valve in the middle. Additionally, the diagram does not show the water filter. It would be located on the cold water (blue) line, immediately after the water pump/city water inlet junction.