Water pump operates from the 12v
system. Flip the switch on the monitor panel. You may have a water pump switch in the bath area too. The water pump will run until it comes up to pressure. When using a faucet the water will run for a few seconds an the pump will come on. When you close the faucet the pump will run a few seconds to build up pressure then stop.
If all the faucets are closed and the pump runs for a second and then repeats within an hour without opening an faucets there is a leak somewhere in the plumbing. Check all the fittings to the faucets. Check the fittings to/from the pump. Check the toilet to see if its leaking and the outside shower faucets.
You can keep the pump on while in the trailer but I always turn it off and run a faucet to reduce the pressure if I'm leaving the trailer for a day trip or while towing.