Your pump hums but no water comes out, it kicks on every few minutes with every faucet closed, or it stays silent when you open a tap. Most RV water pump problems come down to the tank, the strainer, a leak, or 12V power, and you can check all four yourself. This page explains how the pump works, which parts fail, the specs from the makers, and when a pump is worn out.
How does an RV water pump work?
When you are not on city water, a 12V pump pulls water from your fresh tank and pushes it to the faucets, toilet and water heater. Most are diaphragm pumps: a rubber diaphragm moves back and forth while small one-way valves direct the water. It runs only when the system needs water, so it is called a demand pump.
- You switch the pump on. It runs until the lines are full and pressurized.
- The pressure switch turns it off. This small switch on the pump head opens at a set pressure. On the Shurflo 4008 it is 55 psi.
- You open a faucet. Pressure drops, the switch closes, and the pump starts.
- The bypass smooths low flow. On bypass pumps, a spring-loaded valve sends water from the outlet back to the inlet. Shurflo’s opens at about 40 psi, so a trickle runs smoothly instead of stuttering.
- You close the faucet. Pressure climbs and the pump stops. Check valves inside the pump hold that pressure in the lines.
Variable-speed pumps, such as the Remco Aquajet, use an electronic controller that speeds the motor up or down as you open and close faucets.
Which RV water pump parts fail, and what are the signs?
| Part | What it does | Sign it is failing |
|---|---|---|
| Inlet strainer | Catches debris before it reaches the pump | Weak flow, sputtering, or a pump that will not prime |
| Diaphragm | Does the actual pumping | Low flow, or water in the motor end, which Shurflo says points to a punctured diaphragm |
| Check valves | Let water go one way and hold pressure | Pump runs for a second now and then with everything closed |
| Pressure switch | Turns the pump off at a set pressure | Pump never shuts off, or a leak at the switch |
| Motor and thermal breaker | Drive the diaphragm; the breaker cuts power if it overheats | Silent with power present, very hot, or blowing fuses |
| Inlet hose and fittings | Carry water from the tank to the pump | Air bubbles at faucets, or the pump never primes |
| Winterizing valve | Lets the pump draw antifreeze from a jug | Pump runs but pulls air instead of tank water |
What should I check first when my RV water pump stops working?
- Water in the tank. RV tank sensors often read wrong. If you can see the tank, check the water line.
- Switch, fuse and battery. Check the pump switch and its fuse. Shurflo says lower voltage means lower flow, and Remco’s Aquajet stops below 11.5 volts.
- A hot motor. If the pump quit after a long run, let it cool. Shurflo and Remco pumps have a thermal protector that resets by itself.
- Strainer. Unscrew the clear bowl on the pump inlet and rinse the screen.
- Valves. Make sure the winterizing valve draws from the tank and any tank fill valve is closed.
- Leaks. If the pump cycles with every faucet closed, check the faucets, the toilet valve, the water heater and the low-point drains.
Safety first. Turn off the pump and pull its fuse before you touch wires or plumbing. Open a faucet to release pressure before loosening any fitting. Never fit a bigger fuse than the pump’s label or manual calls for. Do not start a pump you think is frozen: Remco warns that running a frozen pump can damage it. Use only RV antifreeze rated for drinking water systems.
RV water pump specs to know
These numbers come from the makers’ spec sheets and manuals. Pumps vary a lot by model, so check the label on yours. We could not find a maker-hosted spec sheet for Seaflo’s RV pumps, so read the label on a Seaflo pump.
| Spec | Shurflo 4008 (12V) | Remco Aquajet ARV | Flojet R3426504A |
|---|---|---|---|
| Power | 12V DC | 12V DC, works from 11.5 to 14.5 volts | 12V DC, works from 9 to 13.6 volts |
| Open flow | 3 gpm | 5.3 gpm | 1.4 gpm |
| Shut-off pressure | 55 psi | 65 psi | 30 psi |
| Flow control | Bypass opens at about 40 psi, full at about 62 psi | Variable-speed controller plus pressure switch and bypass | Internal bypass |
| Current draw | 7.5 amps max; needs at least a 10 amp circuit | 10 amps max | 2.2 amps at 30 psi; 5 amp fuse |
| Dry prime and dry running | Can run dry without damage | Primes up to 14 feet; runs dry | Primes up to 8 feet; runs dry |
| Duty | Intermittent | Intermittent | Intermittent |
| Strainer | Required, 50 mesh | Screen filter required | Required |
Shurflo, Remco, Flojet and Seaflo: how are RV water pumps different?
Shurflo (Pentair) makes the pump in many US RVs. The 4008 is a bypass pump, and Shurflo says it needs no accumulator, a small tank with an air cushion that smooths flow. You can adjust its shut-off with the switch screw.
Remco Aquajet pumps are variable speed and stronger than most stock pumps, so they can draw more current than the pump they replace. Remco says to check your wiring, fuse and any pump controller before you swap one in, and not to adjust the switch without asking the factory.
Flojet and Seaflo also make 12V diaphragm pumps for RVs. Flojet sells an accumulator but says not to use one with a variable-speed pump.
When you replace a pump with another brand, match the voltage, flow, shut-off pressure, fuse size and port fittings. A stronger pump may need heavier wire.
When should you call an RV tech for water pump problems?
- Leaks you cannot reach, such as inside a wall or under the floor.
- Freeze damage to lines, fittings or the water heater.
- A circuit that keeps blowing fuses after you have ruled out the pump, which points to wiring.
- Bypass adjustment. Shurflo says only a technician with proper gauges should change the bypass.
Shops bill by the hour. Many owners swap a pump themselves, so we save tech visits for plumbing and wiring faults.
Common questions
How do I reset my RV water pump?
Most RV water pumps have no reset button. Turn the pump switch off, check the fuse, and if the motor is hot, let it cool: Shurflo and Remco pumps have a thermal protector that resets on its own. Then switch the pump back on and open a faucet to bleed out air.
How do I know if my RV water pump is bad?
Rule out the cheap causes first: tank level, strainer, fuse, voltage and leaks. If the pump gets 12V and stays silent, has water in the motor end, leaks from the head, or still cycles with no leak anywhere, the pump or its valves are worn. Shurflo says scale from skipped sanitizing causes low flow and leak back over time.
Why is my RV water pump running but not pumping water?
It is not getting water or is sucking air. Check the tank, the strainer, the winterizing valve and the inlet fittings. Shurflo also lists air trapped in the water heater, so open a hot faucet until the air clears.
Why won’t my RV water pump shut off?
Water is escaping or the pump cannot reach its shut-off pressure. Check for a dripping faucet, a leaking toilet valve, an empty tank, or an air leak on the inlet side. Shurflo adds low voltage and a bypass set higher than shut-off; Remco adds a tank fill valve left in fill mode. A pump should never run nonstop: Shurflo, Remco and Flojet all rate their pumps for intermittent duty.
Can I bypass the water pump in my RV?
Yes, when you are on city water. The hookup supplies the pressure, so leave the pump switched off. If the fresh tank fills by itself while you are hooked up, Shurflo says scale on the pump valves can let water leak back through.
How do I quiet down an RV water pump?
Shurflo recommends at least 18 inches of flexible high-pressure hose on both ports instead of rigid pipe, and a solid mounting surface. Check that the mounting feet are not loose or squeezed too tight, the strainer is clean, and air is bled from the lines.
How long does an RV water pump last, and what does it cost to replace?
The makers do not publish a lifespan. Shurflo says lack of sanitizing is the number one reason pumps fail early, so sanitize the system and clean the strainer as the manual asks. Pump prices vary by model and labor is billed by the hour, which is why many owners swap a pump themselves.