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How to prime a water pump

Updated: 22 October 2026

The motor runs and the hose stays dry. That is when you look up how to prime a water pump. Priming is the first fill of the casing. A reinforced suction hose and a foot valve are separate jobs. The five pumps on the [domestic water pump comparison](/hub/garden-watering/domestic-water-pump) do not all claim the same start. Peter F., editor for DIY & tools, read those listings on 21 October 2026. There is no laboratory test. If the pipe is a supply pipe, read the [booster pump water regulations](/hub/garden-watering/domestic-water-pump/sub/domestic-water-pump-mains-rules) first. A qualifying purchase can earn a commission at no extra cost to you.

The motor runs and the hose stays dry. That is when you look up how to prime a water pump. Priming is the first fill of the casing. A reinforced suction hose and a foot valve are separate jobs.

Our top picks

VEATON VEATON FGP1200INOX surface pump

Best overall

VEATON VEATON FGP1200INOX surface pump
6.0/10about £79.99
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KATSU Tools KATSU 151414 260 W booster

Best value

KATSU Tools KATSU 151414 260 W booster
5.8/10about £69.99
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KATSU Tools KATSU 151434 150 W self-priming pump

Alternative

KATSU Tools KATSU 151434 150 W self-priming pump
5.1/10about £76.99
View offer
On this page
  1. 1.What priming is, and which listing even claims it
  2. 2.The suction hose has to stay round
  3. 3.Holding the prime
  4. 4.When to stop

What priming is, and which listing even claims it

Never primed usually means the casing was empty or the vertical lift is too great. Lost prime usually means a foot valve or an air leak. The KATSU 151434 states a stop after six minutes without water, and you still fill it the first time. The KATSU 151414 says it is not self-priming. The VEATON says prime before use and drain afterwards. If the page says the pump is not self-priming, go back to the domestic water pump buying guide. Isolate the supply, fill the casing, close it, then restore power.

The suction hose has to stay round

L&S Engineers put a reinforced suction hose on the inlet and layflat hose on the discharge only. Layflat collapses under vacuum and the pump spins on air. The VEATON names a non-return valve and points to a separate 4 metre kit, FPC3-4. The suction figure is 8 metres vertical. Flood & Water Pumps put a practical cap nearer 6 metres. The rainwater layout is on the water pump for a rainwater tank page.
VEATON VEATON FGP1200INOX surface pump

Testsieger

VEATON VEATON FGP1200INOX surface pump
6.0/10about £79.99
View offer

Holding the prime

A foot valve sits at the bottom of the suction line so the column stays up when the motor stops. The flap opens towards the pump, and the valve stays under the water. A valve parked in silt stays open and dumps the prime overnight. A joint that weeps on the outside is often sucking air. Do not keep the motor running while you hunt for the leak. The KATSU 260 W does not get a foot valve as a cure. Use it where water already arrives under gravity.

When to stop

The VEATON’s thermal protection can cut a hot motor. It is not a controller that notices an empty hose. The Ejoyous says it shuts off if inlet water is nearly zero. The Draper names thermal overload and no dry-run time. If the listing is silent, treat any dry running as too long. Stop when the motor hums after a proper fill, when the breaker trips, or when water leaves the casing. A missing plug is electrician’s work. A flooded room is a plumber’s visit.

Common questions

Do I fill a self-priming pump the first time?
Yes. Flood & Water Pumps define self-priming as a casing that clears air after it has been filled once. The KATSU 151434 states that it is self-priming, and you still put water in before the first start. The VEATON tells you to prime before use and drain afterwards, and it does not use the self-priming label. An empty casing on the first morning is how the seal runs dry.
Why does the pump run but move no water?
If it has never worked, the casing was probably empty or the vertical lift is past the claim. If it worked and then stopped, look for a foot valve or an air leak on the suction side. A collapsed garden hose on the inlet produces the same dry outlet. The 8 metre figure is vertical lift, not the hose on the grass. A humming motor is a reason to isolate power.
Can I use a cheap garden hose on the inlet?
L&S Engineers specify a reinforced suction hose on the inlet. Layflat and a soft garden hose belong on the discharge, where the water is pushed. On the suction side they can flatten and leave the pump pulling air. The VEATON does not include that hose. It points to kit FPC3-4. One reviewer’s 30 metre hose was a delivery length after priming, not a suction length.
Where does the foot valve go?
It goes at the bottom of the suction line, under the water, so the column cannot fall back when the motor stops. The flap opens towards the pump. The VEATON names a non-return valve and still expects you to prime. A valve in sludge stays open and the prime is gone by morning. The KATSU 260 W is not self-priming, so a foot valve does not give it a lift it does not claim.
How long may it run with no water?
Only the KATSU 150 W states a number: it stops after six minutes without water and checks again after one hour. That timer is not on the other four. The KATSU 260 W says a dry run may damage the seal and impeller. The VEATON’s thermal cut-out is not a dry-run controller. If your listing gives no time, switch off as soon as the outlet runs dry.
The pump tripped the breaker. Do I reset it and try again?
UK Flow Centre treats a trip, or a motor that only hums, as an electrical stop. Resetting and starting again risks the seal or whatever caused the trip. Isolate the pump until someone qualified has looked. One KATSU 260 W review describes a unit that tripped a breaker. That report is a reason to stop. We do not describe a way to rewire the flex.
When do I stop and call a plumber or an electrician?
Call an electrician when there is no plug, when the breaker has tripped, or when the motor hums after a filled casing. The KATSU 260 W arrives without a plug. Call a plumber when a joint is leaking, when the pump has flooded a room, or when rainwater and a supply pipe could meet. One KATSU 150 W review describes a flood from an unattended start. Stay with the first runs.

Related pages

Best domestic water pump

Domestic water pump

Domestic water pump buying guide: source before watts

Booster pump water regulations UK: the 12 litre notice

Water pump for a rainwater tank: keep it non-potable

Sources

Public UK sources for fittings rules, pump notification, rainwater and plugs. Listing prices, stars and review counts are the saved amazon.co.uk lines. This is not a lab test. One digest source URL for a manufacturer course was truncated and is not listed here.

  1. Water Supply (Water Fittings) Regulations 1999 (retrieved 22.10.2026)
  2. Water Regs UK — pump notification (retrieved 22.10.2026)
  3. Scottish Water — water byelaws (retrieved 22.10.2026)
  4. Water Supply (Water Fittings) Regulations (Northern Ireland) 2009 (retrieved 22.10.2026)
  5. Waterpump.co.uk — increasing house pressure (retrieved 22.10.2026)
  6. Environment Agency — harvesting rainwater for domestic uses (retrieved 22.10.2026)
  7. Electrical Safety First — plugs and fuses (retrieved 22.10.2026)