It's normal for the pump to pulsate. The water pump is preset to keep a more-or-less constant water pressure. When the pump senses a drop in pressure, because you're using water, it runs long enough to restore the pressure and then shuts off. Depending on the demand for water that pressure can be restored rapidly causing the pulsing.

You can install a device called an accumulator tank that will minimize the pulsating.

I think it's a good idea to switch off the pump when not in use... especially when leaving the RV but it is OK to leave it on if you want.

IMPORTANT: If the water pump runs periodically when all faucets are off you have a leak in the water system. The leak may be in the plumbing or it could be in the pump itself. If you are sure that your plumbing is not leaking then the leak is most likely in the pump's internal check valve. This check value is need to keep water from flowing through the pump into the freshwater holding tank when your RV is connected to an external water system. In fact, if you notice that the water level in the freshwater tank is rising it's good sign that the pump is at fault. There are rebuild kits for most water pumps or, depending on how old the pump is, you may want to replace it.

We've been in parks where the water pressure has been very low so we had to use our water pump to boost the park's water pressure to take showers. It works because the pump draws water from the fresh warter tank to supplement that comming from the park.

If the presure of the water comming from the hook-up is less than the pre-set low pressue of your fresh water pump then water will be pumped from your fresh water tank to increase the pressure to that of the pre-set high pressure of the pump. If you do not want to pump water from your freshwater tank turn the water pump off.

The two most common freshwater systems are:

1: A hose connection which bypasses the tank and pump and a separate fill spout used to fill the fresh water tank directly.

2: A hose connection with a valve somewhere near the connection or in a utility area... turn it one way to fill the tank the other way for direct use.

There is a check valve in the plumbing system that permits the outside water supply to charge the system without going into the freshwater tank. There is a check valve inside the water pump and it may be the only one or there may also be an external checkvalve on the discharge side of the water pump.