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How to use a Gardena submersible pump

Updated: 22 October 2026

You are about to lower a pump into a butt, a pool or a puddle, and the box did not include the hose. How to use a Gardena submersible pump is a sequence, not a power figure. Fit the outlet to the water you have, prove the float, then use a 30 mA RCD, and stay with the machine if you have overridden that float. The model rows are on the [Gardena submersible pump comparison](/hub/garden-watering/gardena-submersible-pump). Peter F. used the Gardena UK page, the IET note on Regulation 411.3.3 and the stored instructions. There is no laboratory test. A qualifying purchase can earn us a commission at no extra cost to you.

You are about to lower a pump into a butt, a pool or a puddle, and the box did not include the hose. How to use a Gardena submersible pump is a sequence, not a power figure.

Our top picks

Gardena Gardena 4000/1

Best overall

Gardena Gardena 4000/1
7.3/10about £79.99
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FOTING FOTING 900 W

Best value

FOTING FOTING 900 W
7.2/10about £46.99
View offer
Gardena Gardena clear 20000

Alternative

Gardena Gardena clear 20000
6.2/10about £50.99
View offer
On this page
  1. 1.Set the water and the hose first
  2. 2.Let the float move
  3. 3.RCD, plug and who stays out of the water
  4. 4.When you stop

Set the water and the hose first

These pumps sit in the water and push. You do not prime them. No kept listing includes a full hose. The 20000 models use 25 mm and 38 mm connections. A VEATON adapter may not be a UK hose thread, so try it dry. The 4000/1 uses a 13 mm push-fit on the Screwfix table, and the hose is still not supplied. Open the end before you switch on. Clean rain suits the 4000/1 filter. Grit up to 35 mm is the dirty-water pump or the 2-in-1. That split is on clear water or dirty water. Fit the hose before you lower the pump.

Let the float move

The float needs room to rise and fall. A narrow butt can pin it on the wall. A FOTING review found no park position that lets you wedge it and walk away. Test the arm with the pump unplugged. Automatic mode should stop the pump as the water falls. A tied float is for a shallow residue, and you stay beside it. Gardena UK describes continuous-on on the 4000/1 down to about 5 mm. That is a manufacturer mode. The amazon residual cell is empty, so 5 mm is not a measured leftover. Set the 615 to 815 mm pipe above the sludge. The battery, and the miniature pump's inline switch, stay out of the water. IPX8 on the body does not cover them.
Gardena Gardena 4000/1

Testsieger

Gardena Gardena 4000/1
7.3/10about £79.99
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RCD, plug and who stays out of the water

Use a socket protected by a 30 mA RCD. BS 7671 Regulation 411.3.3, as the IET explains it, requires that for outdoor mobile equipment up to 32 A. NICEIC also says to use a weatherproof socket, not a long extension across wet paving. Confirm a BS 1363 plug, three rectangular pins. Two titles disagree with their article numbers, 09016-47 against 09016-28 and 09017-47 against 09017-28. A European plug is a return. The 18 V charger uses the same RCD, and the battery stays out of the water. Nobody stands in the water while the pump runs. Gardena UK caps the liquid at 35 °C. A hosepipe ban is on the Gardena water butt pump page.

When you stop

Stop when the float cuts the pump out, or, in manual mode, before the inlet sucks air. Switch off before you lift it. Do not retry if the RCD trips at once, or if the casing or lead is damaged. Drying a soaked connector and resetting once is a household check. A trip that returns as soon as you plug in needs an electrician, and so does a new circuit. Part P makes that circuit notifiable. Sewage, or water around indoor sockets, is outside these pumps. A 35 mm passage is not a sewage rating.

Common questions

Do I prime a submersible pump?
No. The pumps in this set are lowered into the water. They are not surface pumps with a priming port. Fit the hose, open the outlet, set the float, and use an RCD. Pouring water into the motor housing is not a start procedure, and the manuals we used do not describe one.
Where does the float have to sit?
Where it can rise and fall without catching the butt wall or the hose. Test that movement with the pump unplugged. Automatic mode should stop the pump as the water drops. If you tie the float up for a shallow residue, stay with the pump. A VEATON note in this set says to stop before a manual run goes dry, and one FOTING review found no safe park for the float.
Can I lock it on and walk away?
Only if the float is free and you are still close enough to hear a problem. Gardena's continuous-on mode on the 4000/1 is specified down to about 5 mm, which is a manufacturer setting, not an invitation to leave the garden. A blocked hose or a float jammed open will let the pump run dry. Locked-on means you remain with it.
What size hose do I need before I start?
The hose is not in these boxes. The Gardena 20000 connections are 25 mm and 38 mm. The 4000/1 is listed by Screwfix with a 13 mm push-fit. A third-party adapter may not match a UK garden-hose thread, so check the fitting before the pump is in the water. Open the far end of the hose before you switch on.
Does the pump need an RCD?
Yes. Outdoor mobile equipment up to 32 A needs a 30 mA RCD under BS 7671 Regulation 411.3.3. Use a protected socket or a known RCD adaptor, and prefer a weatherproof outlet to a long extension across wet ground. The 18 V charger belongs on that same protection. The battery pack does not go into the water.
When do I stop and call an electrician?
When you need a new garden circuit, when the lead or casing is damaged, or when a 30 mA RCD trips again as soon as you plug the pump in. Part P covers a new circuit, and it is not a weekend fitting. Sewage, or water that has reached indoor sockets, is outside these pumps entirely.

Related pages

Gardena submersible pump buying guide

Gardena submersible pump

Best Gardena submersible pump for a rainwater butt

Clear water vs dirty water submersible pump: grit or 1 mm

Gardena water butt pump for stored rain and a hose

Sources

Public UK sources from the research digest, plus the amazon.co.uk prices, stars and review counts captured for these ten listings on 21 October 2026. Last reviewed 22 October 2026.

  1. Gardena UK, rain water tank pump 4000/1 (retrieved 21 October 2026)
  2. Gardena UK, dirty-water submersible pump 20000 (retrieved 21 October 2026)
  3. Gardena UK, 2-in-1 clear/dirty submersible pump 20000 (retrieved 21 October 2026)
  4. Gardena UK, clear-water submersible pump 20000 (retrieved 21 October 2026)
  5. Gardena UK, battery rainwater tank pump 2000/2 18V (retrieved 21 October 2026)
  6. IET Wiring Matters, Regulation 411.3.3 and 30 mA RCDs (retrieved 21 October 2026)
  7. Water Regs UK, alternative water systems (February 2024) (retrieved 21 October 2026)
  8. South West Water, hosepipe ban exceptions (retrieved 21 October 2026)