RV water pumps are "on demand" pumps - once they sense a pressure build up (because the faucets are shut) the pump SHOULD shut off (stop running).
a combination of air & water in the line will still build pressure & should shut the pump off.
usually if the pump isn't shutting off or it runs frequently (even when no water has been used or faucets are shut) then the diaphragm of the pump is probably leaking back and loosing pressure.
the pump diaphragms can be rebuilt, fairly inexpensively & much cheaper than buying a new pump.
