RV Water Pump Not Working or Won't Build Pressure: Fixes

My RV's fresh-water pump won't turn on, won't build pressure, or runs constantly and won't shut off. How do I troubleshoot it?

The 12V fresh-water pump only matters when you're running off the tank (not city water), so first make sure you're actually on tank water with water in it. No-run pumps are usually power (switch, fuse, battery); pumps that run forever without pressure are usually air in the line, an empty tank, or a leak; pumps that cycle rapidly are usually air or a clog. Most are quick checks.

ℹ️ Reference only: For general reference only: AI-assisted and not professional advice. This guide guarantees no result; every situation differs. Verify against the manufacturer, local codes, and a licensed professional before acting, especially for electrical, gas, fuel, plumbing, structural, or roof work. Use at your own risk.

💵 $0 for switch/fuse/air checks; an inlet strainer is $8-$20; a replacement 12V demand pump runs $60-$150. Professional diagnosis/replacement $120-$300. ⏱ 15-45 minutes for checks; ~1 hour to replace a pump. ● Use caution

Safety: Keep 12V electrical connections away from water; if there's standing water near wiring, disconnect power before working. Use potable-safe components and sanitize the fresh system if it's been contaminated or sitting. Don't run the pump dry for long; it can overheat. For storage, winterize to prevent the pump and lines from freezing and cracking.

Common causes

Pump switched off, blown fuse, low battery, or you're on city water. The pump needs its switch on, a good fuse, and 12V; it also does nothing if you're connected to a city-water hookup. (most common)
Quick check: Confirm the water-pump switch is ON, you're NOT connected to city water, the fresh tank has water, and the pump fuse is good. No sound at all from the pump = power or switch.
Empty fresh tank or air in the lines (pump runs but no/low water). After filling or running dry, the pump has to re-prime and push air out. (common)
Quick check: Pump runs but little water comes out: check the tank gauge, then open the highest faucet and let it run to purge air until flow steadies.
Pump cycles on and off rapidly, or runs constantly (won't shut off). Rapid cycling is usually air or a partly clogged strainer/filter; constant running with no pressure is often a leak or a failed pump head/check valve. (common)
Quick check: Listen: rapid click-click-click while a faucet is barely open points to air or a clogged inlet strainer. Constant running with faucets closed means a leak somewhere or a bad pump check valve.

How to fix it

Confirm the basics: water-pump switch ON, fresh tank has water, you're off city water, and the pump's fuse is good. Listen for the pump trying to run.
No sound: check the fuse and the house battery voltage; check the switch and wiring connections at the pump.
Runs but weak/no water: open the highest faucet (both hot and cold) and let it run to purge air and re-prime after filling or running dry.
Rapid cycling: clean the pump's inlet strainer/filter (a clear canister near the pump); debris there makes the pump 'hunt.' Some pumps let you adjust the pressure switch slightly.
Runs constantly with everything closed: you have a leak (check under sinks, the water heater, low-point drains, and the toilet valve) or a failed pump check valve. Find and fix the leak; replace the pump if the head/check valve is bad.
Winter no-run after storage: a pump that was left with water and froze can crack. Inspect for cracks and leaks.
Persistent failure after these checks usually means the pump unit is worn out. A 12V RV demand pump is a straightforward replacement.

DIY or call a pro?

DIY-friendly: switch, fuse, tank, air-purge, strainer cleaning, and even swapping the pump are within reach for most RVers with basic tools. Call an RV tech if you can't locate a constant-run leak, if there's water near 12V wiring you can't safely de-energize, if the freshwater system needs sanitizing after contamination, or if plumbing behind walls/underbelly is involved. A cracked pump or fitting from freezing may need more extensive repair.

Tools & parts

Multimeter (fuse/voltage)
Screwdriver and small wrenches
Replacement inlet strainer/filter
Replacement 12V demand pump (if needed)
Potable-safe plumbing tape/fittings

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Based on: RV water-pump manufacturer (Shurflo, Flojet) troubleshooting and strainer/pressure-switch guidance; General RV-owner guidance on fresh-water systems, priming, and winterization; Potable-water sanitizing guidance for RV fresh systems

General guidance only. If you can't locate a leak, face frozen/cracked plumbing, or have water near electrical wiring you can't de-energize, consult a qualified RV technician. Information here is general reference only and may be estimated or AI-assisted. It is not professional advice. Verify with a qualified professional before acting, and use it at your own risk. See our Terms & Disclaimer.