An RV water pump that keeps running with no fixtures open means water is escaping somewhere in the pressurized side of the plumbing. The leak is most often at the toilet flush valve, the outside shower, a faucet aerator, a hot water tank check valve, or a hidden split line. Less commonly, the pump's internal check valve has failed.
Most likely causes (in order of likelihood)
- Leaking toilet flush valve seal — water drips into the bowl continuously. The #1 cause.
- Outside shower faucet left slightly open or with worn seals.
- Dripping interior faucet, especially under bathroom or kitchen sinks.
- Hot water tank pressure-temperature relief valve seeping.
- Split or cracked PEX line from a freeze event.
- Failed pump check valve allowing back-flow into the fresh tank.
- Loose fitting at the pump or any inline component.
Diagnostic steps (in order, free/cheap before expensive)
- Turn off the pump. Note: if it stays quiet for 2+ minutes, the leak is small. If pressure drops fast and the pump wants to cycle when turned back on, the leak is larger.
- Check the toilet bowl for water trickling in. This is the most common leak. Listen carefully — pour a few drops of food coloring in the tank; if it appears in the bowl without flushing, the flush valve is leaking.
- Open all faucets one at a time briefly, then close them firmly. A faucet not fully closed will mimic a leak.
- Check the outside shower compartment. The faucet may be partially open or seals worn.
- Inspect under every sink with a flashlight. Look for any moisture on fittings or P-traps.
- Check the water heater pressure relief valve (outside, where the heater is mounted). Any drip means the valve or tank is venting.
- Look at the pump itself for any moisture around the inlet/outlet fittings.
- If no visible leak is found, pressurize the system with city water, turn the pump off, and watch for 10 minutes. Wet spots will appear at hidden leak points.
- If the pump runs even with all valves verified closed and no visible leaks, the pump's internal check valve has failed — replace the pump head or the entire pump.
- Verify: Once the leak is found and fixed, the pump should cycle off after building pressure and stay off until a fixture is opened.
DIY vs. call a tech
All steps are DIY. Toilet flush valve replacement is a 20-minute job. PEX line repairs require basic crimping tools but are very forgiving.