Choosing city water or fresh water tank

Normally the switch would be off when connected to city water supply. Sometimes, though, city water pressure is reduced greatly and it works better with pump on drawing from fresh water tank.

If the pump is "on" and the city water pressure falls below the threshold pressure that the pump is set for then the pump will turn on.

mbopp wrote:
If the pump is "on" and the city water pressure falls below the threshold pressure that the pump is set for then the pump will turn on.

X2. Although I never leave my pump on when connected to park water.

The only switch I have is to switch from NORMAL (meaning normal water flow from the park faucet to the trailer) to FILL (meaning fill the fresh water tank from the faucet).

Some newer rigs have a valve set up to switch where the water comes from. Check your water utility compartment to see if your rig has valves there.

Not automatic. It depends on the type of camping you do.

If you put water in the fresh water tank, you will need to use the pump to pressurize the lines in the trailer.

If you are at a campground with water hookups and decide to connect to "city water" by attaching a hose to the inlet, you DO NOT need the pump. The pressure provided by the hose will give you water at kitchen, bath and etc.

Typical RV Trailer water system.
City water connection feds cold water system directly and ties into same cold water line water pump feeds.
Off of the cold water system is a inlet to water heater which then feds hot water system

City water connection has a check valve in it to prevent backflow out connection when using pump.
Pump has an internal check valve to prevent backflow thur pump when using city water.

When connected to city water pump can be ON but wouldn't run due to pumps pressure set point for starting.
IF city water pressure should drop below pump start set point pump would run and supply system until city water pressure recovered. Provided you have water in fresh water tank

I would make two suggestions:
1) get and use a good quality water pressure regulator---WATTS are good and rebuildable. Set it for 50# Static (no flow)
Use it whenever connected to RV...even black tank flush system (different hose....regulator at supply with a 'Y' for the two different hoses.
2) fill fresh water tank and use it/pump vs city water
Had a leak while sleeping and city water connected......flooded RV $6000 PLUS in damages/costs
Now only use pump/fresh water tank cause if a leak happens I can hear pump running
Plus showed up at CG once w/o full fresh water tank and CG water supply main line broken....no water available.

I have a Coleman travel trailer unit and all I do is connect the hose to the trailer city water inlet and turn on the city water. If you are not using the fresh water tank then you don't need to have the pump on. Maybe fancier units have valves that need to be switched but the standard travel trailer to my knowledge does not.

Some people prefer to use only the fresh water in their FW holding tank and only use the built in pump. Their thinking is that it avoids the extremely high pressure in some campgrounds and limits the amount of flooding if they develop a water leak, which is quite common in our "Mobile" homes.

Like most I switch off the pump when hooked to campground water. I do carry fresh water and have use it a time or two when the CG water was kind of funky.

As the diagram shows we have check valves to prevent cross feed, so if the pump was on, it would pump if the CG pressure was low.