The last millimetre is the whole specification
Emptying a pool is a job the filter pump cannot do, and it is the reason a submersible pump ends up in almost every pool shed. The specification that decides this purchase is one that means nothing in any other use: the residual water depth, the film the pump leaves behind when it can no longer draw. Flat-suction models publish it in millimetres — "flachabsaugend bis 1 mm" on the Einhell, and Kärcher builds a whole range on the same claim — and a pump that stops at 35 mm leaves several hundred litres in a large pool, which then has to be swept out. The second figure is the flow rate, 7 500 to 22 000 litres per hour here, with the same caveat as any pump: it is measured at zero head, and a pool being emptied over a wall is working against two or three metres. Then clear water or dirty water, which is a real division rather than marketing: a clear-water pump passes particles of about five millimetres, a dirty-water pump passes twenty to thirty-five, and the second is what an unwintered pool full of leaves needs. The float switch decides whether the pump stops itself; a level sensor decides how low it goes before it does. And the hose connection, usually a stepped adaptor, which is where flow gets lost if the hose is narrower than the outlet. We compare residual depth, flow and head, solids handling, switch type, connection size and cable length.
9 000 l/h, 6 m head, 30 mm solids, G1″ and G1½″
A dirty-water pump handling particles to 30 mm, with 9 000 l/h against 6 m of head, two thread sizes, a quick coupling and a float switch that can be defeated for continuous running.
Best for: Emptying a pool that has been under trees, where leaves would block a flat-suction pump
8 000 l/h, flat to 1 mm, starts at 8 mm, non-return valve
Flat suction to one millimetre with a stated start level of eight millimetres, a mechanical seal, a stepless float switch and an integrated non-return valve.
Best for: Taking a pool down to a film rather than to a puddle
8 000 l/h, 5 m head, 30 mm solids, 7 m cable, IPX8
A 400 W dirty-water pump with 30 mm solids handling, a published seven-metre cable, IPX8, and a submersion depth of seven metres.
Best for: A cellar, a pond and a pool in rotation, where 30 mm and a long cable matter more than the last centimetre
9 000 l/h, 6 m head, flat to 2 mm, 300 W, quick coupling
A 300 W clear-water pump publishing flow, head and pressure together, with flat suction to two millimetres, a stainless steel cover, a triple ceramic seal and a one-handed quick coupling.
Best for: Repeated seasonal draining where the seal and the coupling are worth the price over a generic pump
7 500 l/h, 5 m head, Noryl impeller, 10 m cable
A 400 W dirty-water pump with a Noryl impeller, a mechanical seal, thermal protection and the longest cable in this family at ten metres.
Best for: Repeated use away from a socket, where the ten-metre cable and the thermal cut-out earn their place
9 000 l/h, flat to 1 mm, folding feet, 5 mm particles
A flat-suction pump with folding feet that trade flow against depth: feet out for more delivery, feet in to draw down to seven millimetres and empty to one.
Best for: A small pool or a spill, where taking the last millimetre matters more than lifting it far
17 000 l/h, 10 m head, 1 000 W, 10 m cable, IPX8
The most powerful pump on this shelf: a 1 000 W copper motor moving 17 000 l/h against ten metres of head, with a telescopic handle, a ten-metre cable and IPX8.
Best for: Emptying a large pool quickly, uphill, with something else finishing the last fifteen centimetres
7 300 l/h, flat to 5 mm, 7 m submersion, backflow stop
A clear-water pump with flat suction to five millimetres, a seven-metre submersion depth and a backflow stop that keeps water from running back down the hose when it shuts off.
Best for: Draining a clean pool or a rainwater butt where a hose run downhill would otherwise back-siphon
18 000 l/h, flat to 1 mm, stainless housing, SnapLock
The only pump here that is both flat-suction to one millimetre and rated for dirty water, in a stainless steel housing, with a float-switch control system the maker calls SnapLock.
Best for: Somebody who wants one pump for both the bulk of a pool and the last millimetre of it
Only the specifications at least four models out of five state. A column that is more empty than full compares nothing.
| Model | Price | Amazon reference | Cable length | Connection size | Flow rate |
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Specifications: manufacturer sheets and Amazon product pages. Prices and availability: Keepa. No product on this site has been physically tested.
Most recent revision in this category: September 21, 2026.
