A campervan water pump should normally run when a tap is opened and switch off shortly after the tap is closed. If it continues running, pulses repeatedly or starts when nobody is using the water, something is preventing the system from holding or reaching its normal operating pressure.
The cause may be relatively simple, such as an empty fresh-water tank or air trapped in the pipes. It could also indicate a leak, a damaged connection, an incorrectly charged accumulator or a fault within the pump itself.
Continuously running pumps should not be ignored. Apart from the noise, the pump may flatten the leisure battery, overheat or allow an unnoticed water leak to damage furniture, insulation and electrical equipment.
In this guide, we look at the most common causes and explain a real issue we experienced in our own campervan.
How should a campervan water pump normally work?
Many campervans and motorhomes use a pressure-controlled diaphragm pump.
When a tap is opened, the pressure within the water system falls. The pump detects this pressure drop, switches on and supplies water to the outlet.
When the tap is closed, the pump continues briefly while it rebuilds pressure. Once the pump reaches its shut-off pressure, it should stop automatically.
Depending on the system, there may also be an accumulator fitted between the pump and the outlets. The accumulator stores a small quantity of pressurised water, smooths the flow and reduces how frequently the pump switches on and off.
If the pump cannot build sufficient pressure, it may continue running even though every tap appears to be closed.
First identify what the pump is doing
Slightly different symptoms can point towards different causes.
The pump runs continuously
The pump remains on and never reaches its shut-off pressure. This can happen when it is drawing air, the tank is empty, there is a significant leak or the pump is worn.
The pump switches on and off repeatedly
The pump may run every few seconds or occasionally start for a short period with all taps closed. This usually indicates that the system is gradually losing pressure.
The pump continues briefly after closing a tap
A brief delay is often normal. The pump may need a few seconds to restore pressure, particularly where there is a longer pipe run or an accumulator.
It becomes a concern when it takes an unusually long time, never stops or starts again without any water being used.
Common reasons a campervan water pump keeps running
1. The fresh-water tank is empty
Start with the simplest possibility.
If the fresh-water tank is empty, the pump may continue trying to draw water. Because it is pulling air instead, it cannot build enough pressure to switch itself off.
Do not rely entirely on the tank-level display. Tank sensors can be inaccurate, particularly when they are affected by dirt, scale or the position of the vehicle.
Check that the tank contains enough water and that any tank isolation or drain valves are in the correct position.
Avoid leaving the pump running dry for extended periods. Some pumps tolerate short periods without water, but prolonged dry running can cause unnecessary wear or damage.
2. The water pickup has drawn air
A tank does not necessarily have to be completely empty for the pump to draw air.
When the water level is low, braking, accelerating, cornering or parking on a slope can cause the remaining water to move away from the tank outlet or internal pickup.
If the pump runs while the pickup is uncovered, it may draw air into the pipework. The pump can then struggle to regain its prime and may continue running because it cannot build normal system pressure.
Typical signs include:
- Air spluttering from the taps
- Irregular water flow
- A pump that sounds louder than normal
- The pump running without producing water
- The problem occurring after driving with a low tank
Refilling the tank and bleeding the outlets will often restore normal operation, provided there is no separate fault.
What happened in our own campervan?
We experienced this problem after travelling with a relatively low fresh water level.
Movement of the water while driving appears to have briefly exposed the tank pickup, allowing the pump to draw air into the system. When the taps were opened, air could be heard and seen spluttering through the outlets.
Because the pump had drawn air, it struggled to build its normal shut-off pressure and continued running.
After adding more water and bleeding the air through the taps, the system returned to normal. The pump stopped correctly once pressure had been restored, and it did not continue cycling while the van was stationary.
As a practical preventative measure, we installed an accessible water-pump isolation switch. We now switch the pump off while travelling and when leaving the campervan unattended.
This prevents the pump running unnoticed if:
- The tank pickup becomes exposed
- A pipe or fitting begins leaking
- The pump loses its prime
- The fresh-water tank runs empty
The switch did not remove the air that was already in the system. Refilling and bleeding restored the water supply. The switch prevents the pump from continuing to run unattended if the same circumstances occur again.
Should the water pump be switched off while travelling?
Switching the pump off while travelling is sensible.
It prevents the water system remaining pressurised when nobody is monitoring it and reduces the risk of a pump running continuously because of an empty tank, air entering the pickup or a leak developing.
It is also sensible to switch the pump off:
- When the campervan is unattended
- When the fresh-water tank is empty or very low
- During storage
- Before working on the water system
- When a leak is suspected
The isolation switch should be correctly rated for the pump’s electrical current, installed using suitable cable and remain protected by the correct fuse.
Switching the pump off is a useful safeguard, but it should not be used to disguise a recurring fault. If the pump repeatedly loses pressure when the vehicle is parked, the underlying cause should still be investigated.
3. Air is trapped in the pipework
Air commonly enters a campervan water system after:
- The fresh-water tank has been emptied
- The system has been drained for winter
- The pump has run dry
- Pipework or fittings have been replaced
- The vehicle has travelled with a low water level
- A water filter or strainer has been removed
To bleed the system:
- Make sure the fresh-water tank contains sufficient water.
- Switch the pump on.
- Open a cold tap.
- Allow it to run until the flow is steady and free from air.
- Repeat with the hot side.
- Bleed the shower and any other water outlets.
- Close all outlets and confirm that the pump stops.
Take care if the system includes a water heater. Follow the heater manufacturer’s filling and bleeding instructions before allowing it to heat.
If the air repeatedly returns, there may be an inlet-side air leak rather than a one-off airlock.
4. Air is entering before the pump
The pump may draw air through a small gap on its inlet side.
Possible locations include:
- A loose hose connection
- A cracked pump strainer
- A poorly sealed filter housing
- A damaged tank fitting
- A split or hardened hose
- A missing or damaged sealing washer
- A loose threaded connector
- A kinked or restricted inlet pipe
An inlet-side air leak can be difficult to spot because it may not leak water externally. Instead, the pump draws air inward while operating.
This can produce spluttering at the taps, weak flow and a pump that cannot reach its shut-off pressure.
5. There is a water leak after the pump
A leak on the pressurised side of the system allows pressure to escape. The pump may continue running or repeatedly switch back on as it tries to replace the lost pressure.
Check around:
- The pump outlet
- Push-fit pipe connections
- Tap tails
- Shower mixers
- External shower points
- Water-heater connections
- Tank-filling and drain valves
- Toilet water connections
- Filters and drinking-water taps
- Pipework beneath furniture
Not every leak is immediately visible. Water may travel along pipes, collect underneath cabinetry or enter insulation before appearing elsewhere.
Switch the pump off if a significant leak is suspected, especially where water could reach electrical equipment.
6. A tap or shower valve is not closing properly
A dripping tap or shower mixer can cause the system to lose pressure gradually.
The water loss may be obvious, but some external shower points and mixer cartridges can allow a small internal or external flow that is easily missed.
Check that:
- Every tap is completely closed
- Shower controls are in the off position
- External shower connections are sealed
- Frost-protection and drain valves are closed
- No outlet is slowly dripping
A very small leak may cause occasional pump cycling rather than continuous operation.
7. The pump cannot reach its shut-off pressure
A worn diaphragm, damaged internal valve or ageing pump may still move water but fail to produce enough pressure to activate its pressure switch.
Signs can include:
- Weak water flow
- The pump running for longer than previously
- Irregular pressure
- A noticeable change in the pump’s sound
- The pump working better with one outlet than another
- Gradual deterioration rather than a sudden fault
The pump may require servicing or replacement, depending on its age, condition and availability of parts.
Low supply voltage can also reduce pump performance. A poor electrical connection, undersized cable, weak leisure battery or damaged fuse holder may prevent the pump receiving the voltage it needs under load.
8. The pump pressure switch is faulty or incorrectly adjusted
The pump’s pressure switch tells it when to start and stop.
A failed or incorrectly adjusted pressure switch may cause the pump to:
- Continue running after the taps are closed
- Cycle rapidly
- Stop only when its electrical supply is disconnected
- Start at an unusual pressure
- Produce excessively high system pressure
Some pumps include an adjustment screw, but changing it without first diagnosing the system is not always the correct solution.
Increasing the pressure setting can mask a leak, place additional strain on fittings or exceed the rating of other components. The pump specification and manufacturer’s instructions should be checked before making adjustments.
9. A filter or pipe is restricted
A blocked pump strainer, kinked hose or debris within the system can restrict water reaching the pump.
Possible symptoms include:
- Weak flow from all taps
- A pump that sounds strained
- Longer running times
- Intermittent water supply
- The pump struggling to prime
The strainer should be checked and cleaned as part of routine maintenance. Inspect its housing and seal carefully when refitting it, because a poorly sealed strainer can also allow air into the inlet.
10. The accumulator pressure is incorrect
An accumulator is designed to smooth water delivery and reduce rapid pump cycling. It normally contains an air chamber separated from the water by a diaphragm.
Most accumulators are supplied pre-charged from the factory, but the factory setting may not be correct for the pump fitted to the vehicle. The air charge can also reduce gradually over time.
An incorrectly charged accumulator may cause:
- Rapid pump cycling
- Very little stored water pressure
- Uneven flow
- The pump starting almost immediately when a tap is opened
- The pump operating differently from when the system was first installed
The correct pressure depends on the specific pump and accumulator. Some manufacturers recommend matching the pump’s cut-in pressure, while others specify a setting slightly below it.
The accumulator pressure should be checked with:
- The water pump switched off
- The system fully depressurised
- A tap left open
- A suitable low-pressure gauge connected to the air valve
Air can normally be added using a bicycle or hand pump. Avoid using an uncontrolled high-pressure airline.
If water comes from the accumulator’s air valve, its internal diaphragm may have failed.
An accumulator would not normally introduce air into the taps because its air and water chambers are separated. Air at the outlets is more likely to have entered through the tank pickup, pump inlet or another suction-side connection.
Quick symptom guide
| Symptom | Possible causes |
|---|---|
| Pump runs but no water reaches the taps | Empty tank, exposed pickup, airlock or inlet-side air leak |
| Pump runs and water splutters from the taps | Air in the pipework or air entering before the pump |
| Pump runs continuously with weak flow | Restriction, low voltage, worn pump or air ingress |
| Pump pulses with every outlet closed | Small leak, dripping tap, pressure loss or accumulator issue |
| Pump starts occasionally during the night | Slow leak, non-return valve problem or gradual pressure loss |
| Pump reaches pressure but does not stop | Pressure-switch fault, insufficient pump pressure or incorrect adjustment |
| Pump suddenly sounds louder | Low water, air ingress, restriction or loose mounting |
| Pump works normally after bleeding | Air was likely trapped in the system |
| Air repeatedly returns after bleeding | Check the tank pickup and suction-side connections |
These are possible causes rather than confirmed diagnoses. Several faults can produce similar symptoms.
Can a continuously running water pump damage anything?
A pump that runs continuously can:
- Drain the leisure battery
- Overheat or wear prematurely
- Run dry for an extended period
- Pressurise an unnoticed leak
- Cause water damage inside the conversion
- Create excessive noise and vibration
Turn the pump off if it will not stop normally, then investigate the cause before leaving it running unattended.
When should the water system be professionally checked?
Professional fault finding may be sensible when:
- The pump keeps running after the system has been filled and bled
- Air repeatedly returns to the taps
- The pump cycles while every outlet is closed
- There is evidence of a hidden leak
- Water pressure has become noticeably weaker
- The pump or cabling becomes hot
- The fuse repeatedly blows
- The accumulator cannot hold its air charge
- The installation history is unknown
- Pipework is hidden behind furniture or wall lining
Diagnosis may involve pressure testing, voltage measurements, inspecting the tank pickup, checking pump performance and examining concealed connections.
Campervan water-system fault finding in Blackburn
A continuously running pump is often caused by something straightforward, but repeated pressure loss or air entering the system should be properly investigated.
WeConvert provides campervan and motorhome water-system repairs and fault finding from our workshop in Darwen, near Blackburn. We can assess pump problems, leaking pipework, water tanks, accumulators, taps, filters and existing conversion installations.
We serve customers from Blackburn, Accrington, Burnley, Rossendale, Bolton, Preston and across Lancashire and the North West.
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