Do not start by adjusting the pressure switch. First decide whether the pump has water, whether it can prime, whether a fixture is open, and whether pressure is escaping somewhere.
1. Make sure the pump has water
Confirm the fresh tank has water above the pickup level and the tank drain is closed. If the RV is tilted, a low tank can uncover the pickup. Return winterization valves to normal tank mode and close any siphon tube used for antifreeze.
2. Open a faucet and purge air
Open the nearest cold faucet and let the pump run briefly. If it spits air and then steadies, continue purging other fixtures. If it never produces a steady stream, read RV water pump runs but no water comes out.
3. Inspect the inlet strainer and suction side
A loose strainer bowl, missing O-ring, cracked inlet fitting or loose swivel connection can let the pump pull air without leaking water. Clean the strainer, seat the gasket and tighten by hand as the pump manual allows.
4. Close every water outlet
Check sinks, shower, outside shower, toilet valve, low-point drains, washer hookups, ice maker, spray ports and water filter housings. An outside shower with both knobs open can cause strange pressure behavior even if the wand button is off.
5. Look for leaks while the pump runs
Use a flashlight and dry tissue around fittings. Check under sinks, behind the water heater, around the toilet, near the pump, at filter housings and under the RV. If the pump runs continuously and water appears anywhere, turn it off and fix the leak before testing again.
6. Consider pump check valve and pressure switch issues
If the plumbing is closed, no leak is found, suction is airtight and the pump still never shuts off, the pump may not be reaching shutoff pressure or the pressure switch may not sense it. Internal check-valve debris can also let pressure bleed backward.
7. Do not overtighten the adjustment screw
Some pumps have adjustable pressure switches, but adjusting blindly can mask a leak, overpressure the system or make cycling worse. Use the pump manufacturer's procedure and specifications.
Think of the pump as a pressure detective
An RV water pump shuts off only when it reaches its pressure setting. If it runs continuously, the pump either cannot build pressure or pressure is escaping as fast as it builds. That points to supply, suction air, an open fixture, a leak, a bypass/winterization valve or a pump-head problem.
Quick cause table
| Clue | Likely cause | First check |
|---|---|---|
| Fresh tank low or empty | Pump pulling air | Add water and prime |
| Spitting faucets | Suction leak or air in lines | Strainer bowl, winterize hose and fittings |
| Water flows but pump never stops | Open valve, leak or pressure switch | Close all fixtures and inspect hidden areas |
| No water at faucets | Valve position or pump prime | Check tank valve and winterization valve |
Check every fixture, including the sneaky ones
Outside showers, toilet sprayers, low-point drains, washer hookups, water-panel valves and winterization suction hoses often get missed. A knob left open at an outside shower can let water cross-mix or keep the pump from reaching pressure. A toilet valve can seep quietly into the bowl or tank.
Inspect the suction side carefully
A tiny air leak before the pump can keep it from building pressure without creating a visible water leak. Check the pump strainer bowl, gasket, fittings, winterization tube cap and hose clamps. If the pump sounds faster or raspier than normal, it may be pulling air.
When the pump itself is suspect
If the tank is full, valves are correct, fixtures are closed and no leak is found, the pump check valve, diaphragm or pressure switch may be worn or contaminated. Do not simply turn the adjustment screw until the pump stops; wrong pressure can stress fittings and fixtures. Use the pump manual for adjustment limits.
Related plumbing pages
- RV water pump keeps cycling
- RV water pump runs but no water comes out
- Fresh water tank filling on city water
- Finding hidden RV plumbing leaks
- RV toilet repair guide
FAQ
Why does the pump run after I winterized?
A winterization valve may still be set to the siphon line, the fresh tank pickup may be closed, or air may remain in the lines.
Why does the pump stop only when city water is connected?
City water is supplying pressure that the pump cannot build or hold. Diagnose the pump, suction side, tank supply and leaks.
Can a toilet cause the pump to run nonstop?
Yes. A leaking toilet valve or bowl seal problem can keep pressure from building or holding.
Follow the pump path
The water-system troubleshooter separates no-prime, cycling, leak and pressure-switch symptoms.
Diagnose water pumpCity water and pump problems can overlap
If the pump runs when you are not using city water, the issue is in the pump/tank side or pressure plumbing. But a leaking city-water inlet check valve can let pressure bleed backward, and a mispositioned water-panel valve can send water where it does not belong. If the fresh tank fills while on city water, that is a different clue than a pump that will not stop from the tank.
Use isolation to avoid tearing into walls
If accessible, isolate sections of plumbing one at a time. Turn off the water heater bypass area, close valves to washer hookups, check the outside shower and inspect the wet bay. Place dry paper towels under suspect fittings and leave the pump on only while you are watching it. A slow leak can travel under flooring or into the underbelly before it appears in the living area.
After the repair
Once the pump shuts off normally, leave the system pressurized while you inspect every area again. A fitting that only seeps under pressure can restart the problem later. If the RV has an accumulator tank, confirm its pressure setting matches the pump manufacturer?s guidance; a badly set accumulator can make pump behavior confusing.
More model-specific help
Sources and review notes
Use the installed water pump manual for strainer service, pressure-switch adjustment and replacement parts. RV plumbing layouts vary, especially around winterization valves and water management panels.