How to prime a garden pump
Updated: 22 October 2026
The pump hums, the hose stays empty, and it is easy to decide the motor failed on day one. On the surface pumps in our [garden pump comparison](/hub/garden-watering/garden-pump), that pattern is usually air: an empty casing, or a suction hose that cannot hold a vacuum. This is how to prime a garden pump of that type, and how to tell a seal fault from a machine you should return. Model picks stay on the comparison. The Products Compared editorial team used the Einhell GC-GP 6538 manual, notes from UK Flow Centre, Gardena UK and Waterpump.co.uk, and the stored review themes, as of 21 October 2026. We did not time a prime on a bench.
The pump hums, the hose stays empty, and it is easy to decide the motor failed on day one.
The pump hums, the hose stays empty, and it is easy to decide the motor failed on day one. On the surface pumps in our garden pump comparison, that pattern is usually air: an empty casing, or a suction hose that cannot hold a vacuum. This is how to prime a garden pump of that type, and how to tell a seal fault from a machine you should return. Model picks stay on the comparison. The Products Compared editorial team used the Einhell GC-GP 6538 manual, notes from UK Flow Centre, Gardena UK and Waterpump.co.uk, and the stored review themes, as of 21 October 2026. We did not time a prime on a bench.
Our top picks
| Badge | Product | Before you start | Suction hose | If it runs dry | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Einhell Einhell GC-GP 6538 garden pump | Filler hole and drain screw. Fill before use | No | Overheat guard stated | 8.8 | about £69.95 | View offer |
| Best value |  VEATON VEATON 800 W garden pump with 4 m hose | Fill before first use | Yes, 4 m kit. Reviews dispute the fittings | Listing says do not run dry | 8.4 | about £74.99 | View offer |
| Alternative |  VEATON VEATON FGP1200INOX garden pump | Prime before use and drain afterwards | No. A separate 4 m kit is named | Overheat protection claimed. Wrong use can damage the seal | 8.2 | about £79.99 | View offer |
On this page
Fill the pump before the switch
These surface pumps need water in the casing before they can pull. The Einhell has a filler hole and a drain screw. Its manual says to fill before use, to keep the suction line rising toward the pump, to fit an intake valve, and to open the discharge while you prime. The VEATON 800 W listing says to fill before first use and not to run the pump dry. The VEATON FGP1200INOX listing says to prime before use and to drain afterwards. Wrong use can damage the seal and the impeller.
Unplug before you open a filler plug. Electrical Safety First wants outdoor mains gear on an RCD. Pour clean water in until the casing is full, then close the plug so it seals. Leave the outlet open, into a bucket or an open hose, so trapped air can leave. A shut spray gun holds that air in. If a thermal cut-out trips, let the pump cool, unplug, refill, and try again with the outlet open. You are done when a steady stream replaces the spitting.
Make the suction side hold a vacuum
A full casing still fails if the suction hose leaks air. Air is easier to pull than water, so a loose joint, a missing foot valve, or a hose that flattens will leave the pump spinning on a mixture. Use a reinforced suction hose. Fit a foot valve at the intake so the column stays up when the motor stops. Waterpump.co.uk suggests PTFE tape on the threads. The Einhell inlet is an R1 male of about 33.3 mm, and a snap connector that only sits on the thread will hiss even when it looks tight.
The hose end has to stay under the surface. A foot valve that bobs in the air, or a butt level that drops below the valve, loses the prime. VEATON 800 W reviews include a failure that looks like a bad pump and starts as a bad fit: the supplied hose may not be on the nozzle, because the fittings did not match. If the butt lid is only a hand-sized hole, you may not be able to dunk the hose. That geometry is on garden pump for a water butt. Widen the opening or choose another route. Do not cut the hose into a shape the thread was never meant to take and then blame the motor.
The bucket bubble test
Gardena UK's note on weak flow describes a simple check that transfers to these pumps. Put the suction hose end under water in a bucket, or hold the foot valve under in the butt, and watch while the pump runs with the outlet open. Bubbles from a joint mean air is entering there. A dry floor does not clear the hose. UK Flow Centre notes that an air leak can leave no puddle at all, because the fault is air in, not water out.
If bubbles continue, work back from the pump inlet to the foot valve. Remake the PTFE, replace a split washer, and discard a hose that collapses as soon as the pump pulls. Check that the suction line rises toward the pump, as the Einhell manual asks, so a high loop is not holding air. When the bubbles stop and delivery runs steady, you have a prime. If the flow dies overnight, the foot valve is the first suspect: a valve that does not seat lets the column drain, and the morning start is another empty casing. Fill again, then fix the valve. A bigger pump will not seal a joint that is already letting air in.
When it is not a priming fault
Stop treating it as a prime once the casing is full, the joints are tight, the foot valve is under water and the bubble test is clean, and you still have no delivery. A filler plug that will not unscrew is a parts fault. Unplug first. Forcing it with the lead connected, or cracking the housing, turns a return into a damaged unit. A pump that arrives silent, with a burnt smell or a damaged cable, is a return. The same is true past the stated suction. All three listings print 8 metres, and Waterpump.co.uk puts the practical region around 8 to 9 metres. The 8 metre line is the listing figure, not a promise that 8.0 metres on a hot day will still deliver. Deeper water needs another pump type, which is the split on garden pump vs submersible.
A hum with a full casing and an airtight hose can be a seized impeller, which some VEATON reviews describe in the first weeks. That is a return, not another hour of pouring. Call an electrician if the cable is cut, if the BS 1363 plug or the RCD is damaged, or if the outlet is to be joined into the household plumbing. A Euro plug on many Einhell reviews is a seller issue. This page does not describe a rewire.
Common questions
Where do I pour the water in?
Pour it into the filler on the pump body, with the pump unplugged. On the Einhell that opening is the water filler hole beside the drain screw. The VEATON listings say to fill before first use and do not describe a second place to pour. Fill until water is at the plug, then close it so the joint seals. Filling only the delivery hose leaves the impeller in air.
Why does it lose water overnight?
The column in the suction hose has drained back. A foot valve that does not seat is the usual cause, followed by a joint that weeps air. Refill, remake the valve, and check the hose is still under the water. A butt that has dropped below the foot valve will do the same. Lower the valve, or top the butt up, before you replace the pump.
How do I know the suction hose is leaking air?
Use the bucket test from the Gardena UK note: hose end under water, outlet open, and watch for bubbles while the pump runs. Bubbles mean air is entering at that joint. A dry floor does not prove the hose is tight, because an air leak may never make a puddle. A soft hose that flattens as soon as the motor starts is the same fault. Swap it for a reinforced suction hose.
Can I prime it with the spray gun shut?
Leave the discharge open. The Einhell manual says to open the outlet while priming so air can escape. A shut gun, a closed nozzle, or a kinked delivery hose traps that air, and the pump spins. Prime into a bucket or an open hose end. Fit the gun once a steady stream is there. Holding a transfer pump against a closed nozzle is also a way to overheat a small motor.
When do I stop and return it?
Return it when the casing is full, the suction side holds a vacuum, the lift is inside the stated 8 metres, and there is still no water. Return it too if the cable or housing arrives damaged, or the filler will not open without breaking the body. A Euro plug is a seller matter. Joining the outlet to the plumbing is a job for a qualified person.
Related pages
Sources
Public UK sources from the research digest, plus the amazon.co.uk prices, stars and review counts captured for these three listings on 21 October 2026. Last reviewed 22 October 2026.
- Water Supply (Water Fittings) Regulations 1999, Schedule 2 paragraph 15 (retrieved 21 October 2026)
- Water Regs UK, alternative water systems (February 2024) (retrieved 21 October 2026)
- Electrical Safety First, garden electrics (retrieved 21 October 2026)
- Electrical Safety First, plugs and fuses (retrieved 21 October 2026)
- Einhell UK, GC-GP 6538 (retrieved 21 October 2026)
- Einhell GC-GP 6538 manual (Manuals+) (retrieved 21 October 2026)
- Gardena UK, weak pump flow and the bubble test (retrieved 21 October 2026)
- Thames Water, hosepipe ban FAQs (retrieved 21 October 2026)