Generally, an air leak would be at or before the water pump in the system. If there is a loose fitting, cut in a line before the pump, or an issue with a gasket or valve in the pump, air can be pulled into the system.

Furthermore, if your water pump continuously runs when not in use and you have confirmed that water is available to the pump you most likely have a pressure switch issue. Another Indicator that your water pump may need to be replaced is if it begins to leak.

If the water pump is running but no fluid is being pumped this could be blocked inlet suction filter, check valves failed with pumps bypassing, blocked discharge lines, electric motor polarity is incorrect or incorrect pressure settings parameters amongst other issues.

The humming sound without pumping is a common indicator of the water pump not working in RV. The humming sound is not a major issue. It means there is no water in the water tank. Therefore, add or replace your RV water.