Water pump running constantly.........
Sufficient water level in fresh water tank?
Air leak on suction side of water pump?
Didn't open faucet and purge air out of system?
Water heater filling?
Open low point drain valve?
Water leaking thru city water connection check valve?
Pressure Relief Valve leaking thru?
Toilet water valve leaking thru?
If you have a 'water panel' fill valve in wrong position..water pump just recirculating water from tank thru fill valve back to tank?
Bad pump?