Quick answer: If your pump runs but no water comes out, the problem is usually an obstruction, an airlock, insufficient water at the inlet or too much resistance in the discharge hose. Start by checking the water level, then inspect the strainer and hose for blockages or kinks. Check whether the pump needs priming and whether any non-return valves are obstructing the flow. If it pumps through a short hose but not through your normal installation, the total head may be too high. Always disconnect the electrical supply before carrying out any checks.
You can hear the motor running, but nothing is coming out of the hose. The obvious conclusion is that the pump has failed, although that is often not the case. Some pumps returned to us for suspected faults are not faulty at all, and the issue can relate to the user's pipework or setup. It may be the pump is struggling with an obstruction, an airlock or a discharge arrangement that prevents them from delivering water.
The important thing is to establish whether the pump is failing to draw water in, or whether it cannot push that water out. Both can produce the same symptom, but the solutions are quite different. Before assuming you need a replacement pump, there are a few straightforward checks worth making.
Before you start
Safety first. Switch off and safely disconnect the pump from its electrical supply before lifting, inspecting, cleaning or adjusting it. Never lift a pump by its electrical cable, and never put your hands near the impeller or strainer while the pump is connected to power. If the pump is permanently wired, it must be safely isolated before any inspection or maintenance.
Electric pumps used in wet environments should be connected to a suitable RCD-protected supply. Keep plugs, sockets and electrical connections dry and away from floodwater. Never enter standing water where electrical wiring or equipment may be live. If flooding has affected the building's electrical installation, have it assessed by a qualified electrician before using mains-powered equipment.
The checks below are intended for straightforward mechanical and operational problems. Electrical faults, damaged cables, wiring alterations, repeatedly tripping RCDs and three-phase electrical work must be referred to a suitably qualified and competent electrician. Internal pump repairs should only be carried out by someone competent to do so, and where permitted by the manufacturer's instructions.
Engine-driven pumps must only be operated outdoors because their exhaust gases contain carbon monoxide.
The two-minute checks
Work through these in order. Many problems can be identified without dismantling the pump or undertaking any electrical work. If anything looks damaged or unsafe, stop rather than attempting further restarts.
1. Is there enough water for the pump to work?
Start with the simplest possibility. Is the pump sitting in enough water to operate? Conventional submersible drainage pumps normally require a minimum water depth to maintain flow, and some need the motor or pump casing to remain submerged for cooling. If the water has fallen below the required level, the pump may draw air instead of water.
Automatic pumps introduce another possibility. If the float switch or level sensor is not operating correctly, or is obstructed, the pump may fail to start or continue operating when it should have stopped. Check that any external float can move freely, without reaching into the water while the equipment is energised.
Low-level puddle pumps such as the Tsurumi LSC1.4S and Stream SPK530 are different. They are designed to remove water down to approximately 1mm under suitable conditions, rather than leaving several centimetres behind. However, these pumps must still be correctly primed and operated in accordance with their instructions.
2. Lift it out and check the strainer
Leaves, grit, plastic bags, gravel and other debris can obstruct the inlet. A pump might have been working perfectly for hours before drawing something against the strainer and losing most or all of its flow.
With the electrical supply disconnected, lift the pump using its handle or designated lifting arrangement and inspect the accessible inlet or strainer. Remove any visible debris, taking care around sharp objects and contaminated floodwater. Do not remove protective guards or dismantle internal components unless the manufacturer's instructions specifically permit this.
If the pump is operating in a muddy trench, river or ditch, consider whether it needs to be raised slightly above the sediment on a stable, suitable support. For some applications, a correctly designed mesh basket or additional intake protection can reduce blockages, provided it does not restrict the flow. Low-level puddle pumps are an exception because their purpose is to draw water directly from the surface, so raising them would defeat their function.
3. Walk the hose and check the discharge
A blocked or restricted discharge hose is one of the most common reasons a perfectly good pump delivers little or no water. Follow the entire hose run and look for sharp bends, kinks, crushed sections, closed valves or anything that could restrict the flow.
Layflat hose is particularly vulnerable where it passes over steps, walls or sharp corners. A kink that reduces the internal diameter can create considerable resistance. On the Tsurumi LSC1.4S and Stream SPK530, the discharge connector can be repositioned horizontally or vertically, allowing the hose to leave the pump in a more suitable direction. Any adjustment must be made with the pump safely disconnected, following the manufacturer's instructions.
Also check where the hose discharges. A submerged outlet does not automatically prevent pumping, but it can introduce additional resistance or cause unwanted backflow or siphoning depending on the arrangement. Make sure the outlet is clear, discharges somewhere suitable and cannot allow water to return to the area you are trying to empty.
If the hose has permanently collapsed or cannot maintain its shape along the required route, consider a suitably sized reinforced suction and delivery hose instead.
4. Check for an airlock
An airlock occurs when trapped air prevents the pump from establishing or maintaining the flow of water. The motor may run normally, but the air trapped within the pump casing or pipework stops water moving as intended.
First check whether your pump requires priming, as explained in step six below. Some pumps have a dedicated air-release opening, while others have a particular priming or venting procedure. Often, submersing the pump fully in a bucket of water and running it may clear an airlock.
Where the manufacturer's instructions permit it, a brief restart after correcting the water level, priming or hose arrangement may clear trapped air. However, repeatedly switching a pump on and off without establishing why it is not delivering water can cause overheating or damage. If the pump still produces no flow, switch it off and investigate further rather than leaving it running.
5. Check the non-return valve and any other valves
A non-return valve, sometimes called a check valve, allows water to travel in one direction and prevents it flowing backwards when the pump stops. If it has been fitted the wrong way round, becomes obstructed or jams in the closed position, the pump may run without delivering water.
Check that any accessible valve is installed in the correct direction, normally indicated by an arrow showing the intended flow away from the pump. Also check that any isolation or gate valves on the discharge pipework are open during normal operation.
Some pumps, including low-level puddle pumps, incorporate their own internal check valves. These can become obstructed by grit or debris, but inspection and cleaning should only be undertaken in accordance with the manufacturer's maintenance instructions. Before opening any pipework or valve, isolate the pump and ensure the system is not pressurised.
On the RS32EA pump and AMA Drainer 301, the non-return valve is a small rubber flap. If the pump isn't pumping water, try running the pump without the NRV - if it runs, it is likely you had an airlock.
6. Check whether the pump needs priming
Priming means filling the relevant part of the pump with water so that it can establish suction and begin moving water. Not every pump requires manual priming, but it is particularly important with surface-mounted centrifugal pumps, engine-driven pumps and certain low-level puddle pumps.
Surface-mounted pumps: Certain centrifugal pumps require the casing to be filled with water before starting. Depending on the pump design, the suction pipe may also need filling or a suitable foot valve to retain the water. Check that the suction hose is airtight and designed for suction duty, as an ordinary flexible delivery hose may collapse under vacuum.
Engine-driven pumps: Fill the pump casing through the designated priming opening as instructed by the manufacturer. Check that the suction hose, connections and strainer are suitable and that the suction lift is within the pump's operating limits. Priming time varies with the pump and installation, so do not assume it should always prime within a particular number of seconds.
Low-level puddle pumps: These can also require manual priming, despite being submersible. The Tsurumi LSC1.4S requires approximately 2.5 litres of clean priming water through the discharge coupling when starting with insufficient water in the casing. The Stream SPK530 requires approximately 2 litres through its discharge outlet. Always follow the instructions for your particular model, and never continue operating a pump that has failed to establish flow.
If it still is not right
If the six checks above have not identified the problem, it is worth considering the wider installation. The following faults can produce similar symptoms, although some require professional inspection rather than further troubleshooting by the user.
| Cause | How to tell | What to do |
|---|---|---|
| Head too high or hose too long | The pump delivers water through a short hose but struggles when connected to the normal discharge route. For example, our published LSC1.4S performance figures indicate approximately 170 L/min through 1m of layflat hose, compared with around 20 L/min through 100m, based on a 2m lift. | Check the vertical lift, hose length and internal diameter against the pump's performance curve. Reducing the length, increasing the hose diameter or selecting a higher-head pump may be necessary. See our pump flow rates by hose length. |
| Insufficient or incorrect electrical supply | The pump sounds unusually laboured, runs hot or performs poorly when supplied through a long extension lead, an undersized generator or an unsuitable transformer. | Stop using the pump until the supply has been checked. A competent electrician should confirm the supply voltage, cable suitability and starting requirements. Generators and transformers must be correctly sized for the pump, including starting current. |
| Worn or obstructed impeller | The pump has previously handled sand, grit or abrasive material, and its performance has gradually deteriorated. There may also be unusual noise or vibration. | Inspect only those components accessible through the manufacturer's permitted maintenance procedures. Otherwise arrange professional servicing. Impellers, wear plates and other service parts are replaceable on many pump models. |
| Leaking discharge pipe or hose | Water appears around a hose connection or along the discharge route rather than reaching the intended outlet. | With the pump isolated and the line depressurised, inspect the hose and accessible fittings. Replace damaged hose, clips or connectors as appropriate. Pressurised or permanently installed pipework may require a competent installer. |
| Air entering the suction line | A surface-mounted pump repeatedly loses prime, produces intermittent flow or draws air through a leaking connection. | Inspect accessible suction connections and check that the hose is reinforced, airtight and correctly installed. Check any foot valve or strainer. Stop operation if the pump cannot establish suction. |
| Wrong rotation (three-phase pumps only) | The pump produces unexpectedly low flow or unusual noise from the first operation, particularly following installation or electrical work. | Have a qualified electrician check the phase sequence and direction of rotation using the manufacturer's specified procedure. Any changes to electrical connections must be undertaken by a competent electrician. |
| Wrong voltage or frequency | The voltage or frequency shown on the pump's data plate does not match the electrical supply. For example, a 60Hz-only pump has been connected to a 50Hz supply without the manufacturer's approval. | Stop using the pump. Check the data plate and manufacturer's specifications before reconnecting it. An unsuitable supply can damage the motor and is not necessarily evidence of a defective pump. |
When to stop
Some symptoms suggest a problem that should not be investigated through repeated attempts to start the pump. Switch it off, safely isolate the electrical supply and seek appropriate professional assistance if:
- The RCD or circuit breaker trips when the pump starts, or repeatedly trips during operation.
- The electrical cable, plug or float lead is cut, crushed, damaged or has an unsuitable joint exposed to water.
- The pump gives off a burning smell, makes abnormal noises or becomes excessively hot.
- The motor's thermal protection has operated, particularly following dry running or an obstructed discharge.
- Water contamination is suspected within the motor or seal chamber, including milky seal oil identified during an authorised service inspection.
- There is evidence of electrical damage, exposed wiring or water entering electrical connections.
- The pump continues running without delivering water after the basic checks have been completed.
Maximum flow is not working flow
Where this goes next
Fix it with a spare. If the problem is an accessible, replaceable component, we stock strainers, floats, non-return valves, hose tails and hoses in our fittings and accessories range. Eligible stocked items can be ordered for next-working-day delivery when ordered before 2pm. Always check that replacement components are compatible with your particular pump.
Replace it. If the pump has worn out, suffered irreparable damage or was never suitable for the required head and flow, start with its data plate. Our Pump Finder can help you identify a suitable model, while our guide to finding a replacement pump from an old data plate explains the information you need. Remember that replacing a pump with an identical model will not resolve an installation that requires more head than the original pump can provide.
Claim on the warranty. Manufacturer warranty periods and conditions vary by pump and model. Many Tsurumi submersible pumps and the Stream SPK530 carry a three-year manufacturer's warranty, while other ranges may differ. Warranties generally cover qualifying manufacturing defects rather than normal wear, accidental damage or misuse, and any exclusions will depend on the applicable manufacturer's terms. If you believe your pump has developed a fault, begin with the form on our troubleshooting page. You can also read our warranty information for details of the process.
Order online, or by phone. Browse our range of water pumps and accessories online, or contact our UK-based team if you need help identifying a suitable replacement. Order eligible stocked products before 2pm for next-working-day dispatch.
Important safety information: This guide provides general troubleshooting information and does not replace the manufacturer's operating instructions or an assessment by a competent professional. Only undertake checks that can be carried out safely. Electrical installation, testing and repairs must be undertaken by suitably competent persons. If you are uncertain about the condition or safety of a pump or its electrical supply, disconnect it where safe to do so and seek professional assistance.
