Tom,
To determine what pressure your water pump is rated for, just read the pump label and go to the manufacturer's web site for the specifications. There is a low chance that a 11 year old coach has the original water pump.
If your water pump is turned on when you are on city water, when you open a facet, you will get water from the highest pressure source. So if your city water supply is at 65 PSI and your water pump is rated at 45 PSI, your water usage will be from the city water supply unless the city water pressure drops below the pump pressure due to a high GPM usage. However if the pressure reading are reversed with the pump having a higher pressure, you will be using tank water.
Gerald