Hello Crocodile,
Unless your van is fitted with a device to detect mains water pressure and therefore disable the pump, I would imagine the pump needs to remain OFF. When turning the water on and connected to mains, the pump should not be operating ie you should not be able to hear it or feel it if you put your hand against it. Having the pump ON somehow defeats the purpose of being connected to mains. If your van is such that it retrieves water from the tanks and tops up the tanks as you use the water, then this is another matter altogether. However, I do not believe a van manufacturer would set up such a complex system. Then again, I stand corrected.
We are looking at upgrading our van to a Golden Eagle or a Paramount, could you please name the dealer in question. If you do not wish to publicise the name on the forum, please PM me. Thank you
Larry

Theoretically the pump should be off, but in most cases the mains pressure would be sufficient to overcome the pressure of the pump. This will keep the non return valve on the outlet of the pump closed, which will in turn keep the pressure switch of the pump in the off condition and the pump stopped no matter whether the switch is on or off. If the pump tends to run when on mains, then turn it off.

Your system should have a one way valve which is opened when connected to mains, opened by the mains pressure, and is closed when not connected therefore you need to then turn your pump ON when NOT connected but OFF when you are.

So much to learn, so little time to learn it all.

Bob

The problem with not turning the switch off is if the mains pressure is low enough then the pump will drain your tanks in preference to the mains supplying your water. If you could rely on the mains pressure exceeding the pump pressure then their may not be the need to switch it off.

THe Pump should be OFF. The mains pressure system will bypass the tanks, and will not affect them (even if they are empty) Filling your tanks should be from a different inlet . If you're connected to mains pressure and the 12volt pump is OFF, then turning a tap on should give you a flow. You should not need any electrical power at all to operate water flow under mains pressure.

I only have one infill point on my Coach, I connect the hose. It has a non return valve at the connection, Its built into the Coach, It cant be removed,

I turn the Tap on, First it fills the Tanks when I open the Valve in the front of the Coach, The tank over flow, when its full, 90 Gallons later, It flows out the over flow, I turn that valve off,

Then the Coach has a pressurised tank with Fresh water, Turn any of the the taps on, it is mains pressure,

Turn the Tap off and disconnect the hose, Its water pump pressure, Which is no different from the Mains Tap Pressure,

I dont know as yet, as I havent tried it, Whether the Tank fills up if I dont open the over flow Valve,

I dont think it would, as it is an over flow pipe on the top of the tank,

I have no idea on where the tank gets filled up from, If its into the top of the tank, It will disperse the air and fill the tank, No it wont, It gets sucked out from the bottom of the tank, so it will actually accumulate trapped air inside the tank,

Sorry, Thinking on paper,

Its all automatic, I dont touch any thing except The over flow valve when required, and connect the hose.

Its all very simple connections, Mechanically, About as basic as you can get, But it does work very effectively,

It does have some sort of solenoid thingy sitting on top of the water pump,

I would suggest at this point in time, That its a Pressure Cut Off switch to protect the water pump,

How it works, I havent a Clue, Zip, Ditto, Total Dummy, No Idea,

Not sure about anybody else, I switch mine off when on mains. Seems a waste to me to have it on. Happy Travels..

I leave my water pump switch on even if connected to mains water at a caravan park, which I am in very rarely. The reason that I leave it on is that the one switch controls both the drinking water and wash water pumps, and we still use the drinking water as it is filtered water of known origin and quality. The wash water pump, although it has power to it, won't operate due to the pressure of the mains water keeping it switched off.