RV OWNER’S FIELD GUIDE · PLUMBING
Fresh Water Pump Troubleshooting
The demand pump is one of the most-replaced parts on an RV, and one of the most often replaced unnecessarily.
Pump Runs Constantly, Won’t Shut Off
This almost always means the pump can’t reach its cutoff pressure — a leak somewhere in the system (even a slow one), an open faucet, or a failing check valve letting pressure bleed back. It’s rarely the pump itself; chasing a leak first saves a needless replacement.
Pump Won’t Prime
A pump that runs but moves no water has usually lost its prime — air in the line, a nearly empty tank, or a suction-side fitting drawing air instead of water. Filling the tank fully and running the pump with a faucet open sometimes re-primes it; if not, the check valve or suction line itself needs inspection.
Rapid On/Off Cycling (Chatter)
Fast, repeated cycling under normal use points to a waterlogged or failed accumulator tank if your system has one, or a pressure switch losing its calibration. This is a common, inexpensive fix that’s often mistaken for a pump replacement.