Modern RV’s have internal water tanks and pumping systems, but these are incompatible with city water supplies as these run at a high pressure.
Modern RVs are equipped with pressure demand type automatic pumps, polyethylene fresh water storage tanks, and polybutylene water lines. These systems are designed to be operated at a certain maximum water pressure level in the neighborhood of 35 to 45 pounds per square inch. The on-board pump has a built in pressure switch that shuts off the power to the pump when this pressure has been reached.
However, there is a city water connection to supply water at home or at the RV park via a hose connection. Often, the pressure at these facilities exceeds 80 pounds per square inch or more, sometimes much more, in certain situations. This high pressure can and does cause leaks to develop where none had come before and chances are god that’s when you are either out to dinner or it’s 3 in the morning.
A simple device is available and necessary for your peace of mind. A water pressure regulator should be used whenever connecting to an outside water supply source. This device controls the incoming water pressure to supply a continuous and regulated 45 PSI maximum. It is connected at the supply end of the hose to protect the hose and the RV at the same time. You can find it at your local RV supply store.