RV water pump not working? Here's the fix.

Before you call a mobile tech at $150 an hour, walk through these seven checks. Nine times out of ten, one of them is the problem.

An RV water pump that won't prime, won't turn off, or pulses like a heartbeat is one of the most common calls mobile RV techs get. The good news: most of the time, it's something simple. This guide walks you through the exact checks a tech would run, in the order they'd run them.

1. Is the pump switch actually on?

Sounds obvious, but it's the most common "fix" on a service call. The water pump switch is usually on a panel near the door, in the bathroom, or near the kitchen sink. Flip it on. You should hear a clicking sound as the pump cycles up.

If you hear nothing at all, skip to step 5 (fuse check). If you hear clicking but no water, keep going.

2. Check your fresh water tank level

The onboard pump can only pull from your fresh water tank. If the tank is empty or down to a splash, the pump will suck air, lose prime, and sound like it's running but produce no water.

Check your tank monitor panel. If it reads low or empty, fill the fresh tank from a potable water source and try again.

3. Check the 12V house battery

RV water pumps run on 12V DC, not shore power. If your house battery is dead or weak, the pump may click weakly or not respond at all. Plug into shore power and give it a few minutes, then try the pump again. If it wakes up, your battery is the real problem, not the pump.

4. Open a low faucet to bleed the air

If the pump is running but not producing water, there's air trapped in the lines. Open the closest cold water faucet and let it run. You'll hear sputtering and see air bubbles before a steady stream comes through. This re-primes the pump.

If you've been boondocking and your tank ran dry at some point, you almost always need to do this step after refilling.

5. Check the pump fuse

If the pump is completely silent with the switch on, check the 12V fuse panel. There will be a fuse labeled "Water Pump" or "WTR PMP." Pull it and inspect the metal strip. If it's broken, replace it with the same amperage fuse. You can find these at any hardware store or RV shop.

If the new fuse blows immediately, stop. Something in the pump circuit is shorted and you need a professional.

6. The pump keeps cycling on and off (pulsing)

If the pump turns on and off by itself every few seconds when no faucet is running, you have a leak somewhere in the pressurized plumbing. The pump is building pressure, the leak drops the pressure, and the pump kicks back on to compensate.

Check under sinks, behind the toilet, in the water heater compartment, and outside at the city water inlet. Look for drips, damp spots, or water stains. A common culprit is the toilet water valve or a loose fitting at the water heater.

7. Did you recently de-winterize?

If your rig was winterized over the off-season, there's a bypass valve on the water heater and sometimes a second valve that pulls antifreeze from a jug instead of your fresh tank. If these valves are in the wrong position, the pump will never pull from your tank.

Find the bypass valves (usually behind an access panel near the water heater) and make sure they're all set to "normal" or "summer" mode.

Winterization and de-winterization pump issues

The most common spring problem is a water pump that was working fine last fall but won't work now. If your RV was winterized with antifreeze, the pump may have antifreeze in the lines but no actual water to push. De-winterize first: close the water heater bypass valve (this is critical, many people forget it), connect to city water or fill the fresh tank, and open each faucet one at a time until clear water flows. Then switch to the pump. If the pump runs but no water comes out, the bypass valve is still in the winterize position, diverting water around the heater and back into the tank. See our seasonal prep checklist for the full de-winterization procedure.

When to replace vs repair your RV water pump

RV water pumps (Shurflo and Flojet are the most common brands) are not designed to be repaired at the component level. If the pump runs but produces no pressure, the internal diaphragm has likely failed and the whole pump needs replacing. A new Shurflo 4008 (the most common RV pump) runs 50 to 80 dollars. Replacement takes about 30 minutes with a screwdriver and two hose clamps. Match the flow rate (3.0 GPM is standard for most rigs, 5.0 GPM for larger fifth wheels with multiple bathrooms). If you are upgrading, also consider adding an accumulator tank, which smooths out pressure pulses and reduces pump cycling.

When to call a mobile RV tech

If you've worked through all seven checks and still have no water, it's time for a professional. Symptoms that mean "call now, don't keep tinkering":

• Fuse blows every time you reset it
• Pump runs but makes a loud grinding or screaming noise
• You found a leak but can't identify the source
• You smell burning plastic or see smoke from the pump compartment

Open Camphost and tell it your location, it will help you find mobile RV techs in your area.

Frequently asked questions

Why won't my RV water pump prime?

The most common cause is an air leak on the suction side of the pump or an empty fresh water tank. Check that the tank actually has water, that the winterize valve is in the normal position (not bypass), and look for loose fittings between the tank and the pump inlet. A pump can't pull water if it's pulling air.

Why does my RV water pump run constantly without anyone using water?

A constantly running pump means it can't reach its cutoff pressure, which usually points to a leak somewhere in the plumbing or an open faucet. Check every faucet (including the outside shower and toilet), look under sinks for drips, and inspect the water heater bypass valves. A small drip is enough to keep the pump cycling.

Why does my water pump pulse on and off when I open a tap?

Pulsing usually means a worn pressure switch or a failing accumulator. The pump is supposed to maintain steady pressure, but when the switch wears out it cycles rapidly. Try adjusting the pressure switch screw on top of the pump as a temporary fix. Long term, replace the pump or add an accumulator tank.

Should I use my water pump when hooked up to city water?

No. When you're on city water (a hose into the city water inlet), the pump should be off. The pump only pulls from the fresh water tank. Running it while hooked up wastes battery and can damage the pump if there's no water flow.

How long does an RV water pump usually last?

Most Shurflo or Flojet 12V RV pumps last 5 to 10 years of seasonal use. They fail more often from sitting unused (rubber diaphragms dry out) than from heavy use. If your pump is over 7 years old and starts pulsing or losing pressure, it's near end of life.

What PSI should my RV water pump be set to?

Most RV water pumps come preset to 40 to 55 PSI. The sweet spot for most rigs is 45 PSI. If your pump has an adjustable pressure switch (a small screw on the pump body), you can fine-tune it. Too high and fittings may leak. Too low and the shower will feel weak. If you are getting inconsistent pressure, adding an accumulator tank (25 to 40 dollars) smooths out the surges.

Why does my water pump cycle on and off?

Short cycling (pump turns on for a second, off for a second, repeatedly) means air in the lines or a small leak somewhere in the system. First, open a faucet and let the pump run for 30 seconds to purge air. If it still cycles, check for dripping faucets, a running toilet flapper, or a leak under the rig. A very common cause is a small crack in the pump's check valve, which lets water slowly bleed back and triggers the pump to kick on again.