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Submersible tank pump with float switch: comparison

Updated 11 Oct 2026 · WaterTally

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Submersible tank pumps work under water and do not need priming. The sample contains three very different types, not to be confused:

Low-head barrel and tank pumps (Gardena 4000/1, Einhell GE-SP 3546 RB, Kärcher BP 1 Barrel): up to 11–13 m. Suitable for transferring water or for watering at low pressure.
Multi-stage pumps (Gardena 4700/2 inox, Einhell GC-PP 900 N, Kärcher BP 2, DAB Divertron 900): heads from 23 to 45 m. They are for sprinklers or for lifting water from further down.
Clean-water drainage pumps (DAB Nova 300 M-A, Pedrollo TOP 2): high flow at a few metres. They empty well, but give no pressure.

What to look at

Head at the flow you need, not the maximum flow: for the Gardena 4000/1 the manufacturer gives 2,900 l/h at 5 m against the 4,000 on the box. See maximum flow and real flow.
Float switch: it switches the pump off when the water is low. The Divertron 900 in this comparison has none; DAB sells versions with a float switch as separate models.
Particle size: the maximum size of solids the pump can take in. It matters with rainwater, which carries sediment.
Immersion depth: how far below the water surface the pump can sit, not the depth of the well or tank.

Upper limits declared by Kärcher as “<” are shown as the maximum value. The calculator keeps pumps with a curve separate from those with maximum values only. To connect the tank to your system, see the guide on pumps for tanks and rainwater.

Your system

The water

Depth of the water level below ground (m)From ground level, the same reference as the outlet height. Above-ground tank or water at ground level: 0.

How do I measure it?

Lower a weighted string until it touches the water, with the pump off, and measure the distance from ground level. If you measure from the well rim, subtract the rim’s height above the ground: otherwise the depth comes out larger than it is. Repeat after drawing water for a while: the level drops while pumping, and the lowest one counts.

Where it has to go

Height of the outlet above ground (m)The highest point to reach: sprinkler, tap, raised tank.

Pressure needed at the outlet (bar)0 if the water flows out freely, for example into a tank.

Where do I find it?

For sprinklers and drippers it is in the datasheet, in the flow–pressure table of the nozzle you will use. For a plain garden tap you can enter 0.

The delivery hose

Delivery hose length (m)

Hose inner diameter (mm)

Where do I find it?

Use the inner diameter, not the outer one. Garden hoses sold as “1/2 inch” are usually about 13 mm inside and “3/4 inch” about 19 mm, but it varies: check the hose datasheet or measure it.

How much water you need

Flow you need (l/min) (optional)Sum of the flows of the sprinklers running together.

Work it out with a bucket and stopwatch

Litres collected

Seconds taken

Result

Enter depth, height, hose length and diameter and pressure to see the estimates.

Curves “read from the manufacturer’s chart”: points read from a published chart, not a table, rounded to the precision of the reading. For these pumps the calculation uses the lowest and the highest curve the reading allows: the flow is a range, and “enough” or “not enough” holds only if it holds for the whole range. The same applies to reaching the head. “Declared” curves: points published by the manufacturer. “Max values only”: the manufacturer gives only maximum flow and head, joined by a straight line: an indicative estimate, not a confirmation. Depth and height are measured from the ground: the lift is their sum, and for surface pumps the depth is compared with the maximum suction depth as if the pump stood at ground level. Assumptions: clean water at 20 °C; smooth hose (roughness 0.007 mm, a high value for PVC and PE); fittings, bends, filters, valves and the suction hose are not included, so real flow will be lower. For surface pumps the real suction depth is lower than declared with a long or narrow suction hose. No extrapolation beyond documented points. This is a hydraulic estimate, not a system design. How we calculate and what we do not know

Product	Declared maximum flow	Declared maximum head	Maximum immersion depth	Float switch	Declared input power	Maximum particle size	Where to find it (ad)
Gardena Rain water tank pump 4000/1 (item 1762-20)	4,000 l/h ^[26][28]	13 m ^[26][28]	7 m ^[26]	✓ ^[26]	400 W ^[26]	not documented	Ad · view the product at: Amazon; Ad · search for the model at: ManoMano
Gardena Tank pump 4700/2 stainless (item 1764-20)	4,700 l/h ^[27][28]	23 m ^[27]	7 m ^[27]	not documented	550 W ^[27]	not documented	Ad · view the product at: Amazon; Ad · search for the model at: ManoMano
Einhell GE-SP 3546 RB (item 4170438)	4,600 l/h ^[29][30]	11 m ^[29][30]	7 m ^[29][30]	✓ ^[29]	350 W ^[29]	2.5 mm ^[29][30]	Ad · search for the model at: Amazon · ManoMano
Einhell GC-PP 900 N (item 4170964)	6,000 l/h ^[31][32]	32 m ^[31][32]	7 m ^[31][32]	✓ ^[31][32]	900 W ^[31][32]	not documented	Ad · search for the model at: Amazon · ManoMano
Kärcher BP 1 Barrel (1.645-460.0)	3,800 l/h ^[33]	11 m ^[33]	7 m ^[33]	✓ ^[33]	400 W ^[33](rated input power)	not documented	Ad · view the product at: Amazon; Ad · search for the model at: ManoMano
Kärcher BP 2 for tanks (1.645-420.0)	5,700 l/h ^[34]	32 m ^[34]	7 m ^[34]	✓ ^[34]	800 W ^[34](rated input power)	not documented	Ad · search for the model at: Amazon · ManoMano
DAB Divertron 900 (900 M, single-phase)	not documented	45 m ^[35][36]	12 m ^[35][36]	✗ ^[35]	not documented	3 mm ^[36]	Ad · view the product at: Amazon; Ad · search for the model at: ManoMano
DAB Nova 300 M-A (single-phase, with float switch)	not documented	not documented	7 m ^[37]	✓ ^[37]	350 W ^[37]	not documented	Ad · search for the model at: Amazon · ManoMano
Pedrollo TOP 2 (single-phase, 0.37 kW at the shaft)	not documented	not documented	3 m ^[38]	✓ ^[38]	not documented	10 mm ^[38]	Ad · search for the model at: Amazon · ManoMano

Sources

Water - Dynamic (Absolute) and Kinematic Viscosity — The Engineering ToolBox, retrieved 11 Oct 2026
Surface Roughness Coefficients — The Engineering ToolBox, retrieved 11 Oct 2026
Pompa per cisterna 4000/1 — GARDENA, retrieved 11 Oct 2026
Pompa per cisterna 4700/2 inox — GARDENA, retrieved 11 Oct 2026
Regenfasspumpe / Tauchpumpe 4000/1, 4700/2 inox, 4700/2 inox automatic - Betriebsanleitung — GARDENA, retrieved 11 Oct 2026
GE-SP 3546 RB - Istruzioni per l'uso originali — Einhell, retrieved 11 Oct 2026
GE-SP 3546 RB - dati tecnici — Einhell, retrieved 11 Oct 2026
GC-PP 900 N - Istruzioni per l'uso originali — Einhell, retrieved 11 Oct 2026
Einhell GC-PP 900 N — Einhell, retrieved 11 Oct 2026
BP 1 Barrel - scheda prodotto — Kärcher, retrieved 11 Oct 2026
BP 2 per Cisterne - scheda prodotto — Kärcher, retrieved 11 Oct 2026
Divertron - pompe sommerse multigiranti, scheda tecnica — DAB Pumps, retrieved 11 Oct 2026
Divertron - manuale d'istruzioni — DAB Pumps, retrieved 11 Oct 2026
Nova - pompe sommergibili per acque chiare, scheda tecnica — DAB Pumps, retrieved 11 Oct 2026
TOP - elettropompe sommergibili da drenaggio, 50 Hz — Pedrollo S.p.A., retrieved 11 Oct 2026
BP 2 Cistern, istruzioni per l'uso originali (59910160, 02/22) — Alfred Kärcher SE & Co. KG, retrieved 12 Oct 2026
BP 2 Cistern, istruzioni per l'uso originali (59661830, 08/13) — Alfred Kärcher GmbH & Co. KG; copia ospitata da media.hornbach.ch, retrieved 12 Oct 2026
BP 1 Barrel, istruzioni per l'uso originali (59910220, 02/22) — Alfred Kärcher SE & Co. KG, retrieved 12 Oct 2026