RV Water Pump Runs but No Water Comes Out
If your RV water pump runs but little or no water reaches the faucets, the pump itself may not be the problem. Fresh-water level, valves, strainers, air leaks, winterization settings and plumbing restrictions can all prevent normal water flow.
How an RV Water Pump Works
The RV water pump pulls water from the fresh-water tank and pushes it through the plumbing system until the system reaches the pump's pressure-switch setting.
When you open a faucet, pressure drops and the pump starts again. When the faucet closes and pressure is restored, the pump should shut off.
If the pump continues running without moving water, something may be preventing it from drawing water, building pressure or both.
Common Reasons the Pump Runs but No Water Flows
Fresh Tank Is Empty
Tank gauges can be inaccurate. Verify that there is actually enough water in the fresh-water tank for the pump pickup.
Winterization Valve Position
A winterization or siphon valve left in the wrong position can cause the pump to draw air instead of water from the fresh tank.
Clogged Pump Strainer
Debris in the inlet strainer can restrict water flow and keep the pump from receiving enough water.
Suction-Side Air Leak
A loose fitting, cracked hose or damaged seal before the pump can allow air into the line and prevent proper priming.
Low 12V Voltage
Weak voltage can cause a pump to run slowly or fail to develop its normal pressure and flow.
Pump Problem
Internal check valves, diaphragms, pressure-switch components or other pump parts can wear or fail.
Start With the Fresh-Water Tank
Before replacing the pump, confirm that the fresh-water tank contains water.
RV tank monitors are useful indicators but can give incorrect readings. If possible, verify the actual water level rather than relying only on the monitor panel.
Check the Winterization and Water-Valve Positions
Many RVs have valves used for winterization, tank filling, sanitizing, city-water operation or selecting different plumbing modes.
If one of these valves is left in the wrong position, the pump may pull air from a winterization hose instead of pulling water from the fresh tank.
This is particularly common after winterization or de-winterization.
What We Check During an RV Water-Pump Diagnostic
- Actual fresh-water tank level
- Water-system valve positions
- Winterization or siphon-valve position
- Pump inlet strainer
- Visible suction-side plumbing and fittings
- Air leaks before the pump
- 12V voltage at the pump
- Pump electrical connections
- Water flow at the pump inlet and outlet
- Whether the pump can prime and build pressure
The goal is to determine whether the problem is before the pump, inside the pump or somewhere in the plumbing after the pump.
Why a Pump Can Run Without Pumping Water
RV water pumps are designed to move water, but they cannot build normal pressure if they are continuously pulling air into the inlet line.
A loose fitting can sometimes allow air into the suction side without producing an obvious water leak because that section of plumbing is under suction while the pump is operating.
That is why checking for water leaks alone may not reveal the problem.
What If the Pump Will Not Prime?
A pump that has lost its prime may run without drawing water from the tank.
The diagnostic process should include confirming water is available at the pump inlet and checking for restrictions or air entering the inlet plumbing.
If the pump receives water but still cannot move it or build pressure, the pump itself may require further evaluation.
What If Water Comes Out but the Pump Never Shuts Off?
That is a different symptom.
A pump that delivers water but continues running may be dealing with a plumbing leak, pressure loss, low flow, improperly adjusted pressure switch, pump problem or another condition preventing the system from reaching shutoff pressure.
What If the Pump Works but Only One Faucet Has No Water?
If other fixtures have normal water pressure, the pump is less likely to be the cause.
The problem may instead involve the individual faucet, aerator, valve, supply line or another restriction affecting that fixture.
Mobile RV Plumbing Diagnostics
MilTech RV provides mobile RV plumbing diagnostics and repairs for water pumps, freshwater systems, faucets, toilets, leaks, valves, city-water connections and related plumbing problems.
Learn more about MilTech RV Plumbing Repair & Leak Diagnostics →
Service Areas
MilTech RV provides seasonal mobile RV service in Greater Des Moines, Iowa and Yuma, Arizona .
RV Water Pump Running but No Water?
Tell us your RV year, make and model, whether the fresh-water tank contains water, whether the pump runs continuously, and whether you recently winterized, de-winterized or changed any plumbing valves.
Request RV Service Call/Text 515-257-6021