The different centrifugal impellers

How does an impeller work?

Almost all submersible pumps are centrifugal pumps. The motor makes an impeller with blades rotate. Water enters at the center (the 'eye') and is flung outwards by centrifugal force, towards the outlet. The shape of this impeller determines how much water the pump moves, how efficiently it does so, and how large the solid parts can be that come along.

An overview of impeller types

Channel impellers: open, semi-open, and closed

Open impeller: the blades are open on both sides. Simple and inexpensive, but less strong and more susceptible to cavitation. It is mainly found in smaller pumps for clean water.

Semi-open impeller: the blades are reinforced with a plate at the rear. A good compromise between efficiency and insensitivity to dirt. The clearance between the blades and the pump housing must remain small, otherwise efficiency decreases.

Closed impeller: the blades are enclosed between two plates. This provides the highest efficiency and pressure, but the narrow channels clog quickly. Therefore, it is primarily suitable for clean water, such as with borehole pumps.

Vortex impeller: the choice for dirty water

A vortex impeller is set back in the pump housing. It creates a vortex that moves the water, while solid parts largely flow past the impeller rather than through it. This means it rarely clogs and wears less due to sand and sludge. The disadvantage is lower efficiency: you need slightly more power for the same flow rate. Choose vortex if your water contains fibers, leaf debris, sludge, or small solid parts.

Example: the Pentair U3K(S) and Simer 6 have a vortex impeller and are therefore insensitive to lightly contaminated water in a basement or pit.

Cutting mechanism: for toilet water and thin pipes

A pump with a cutting mechanism has blades that finely grind solid parts before they enter the pump. This allows toilet water to pass through a pressure pipe of only a few centimeters. This is useful for renovations and long piping routes. A cutting mechanism does require some back pressure to function properly, and the blades need to be replaced over time. If you have space for a thick pressure pipe, a pump with a large free passage is often simpler.

Which pump belongs to which impeller?

VORTEX – LIGHTLY CONTAMINATED

Pentair Jung U3K(S)

For basement and pump pit, with float and 10 m cable.

€425.49

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VORTEX / SINGLE-CHANNEL – WASTEWATER

HOMA TP48 (50 mm passage)

50 mm free passage for coarse wastewater, choice of impeller type.

from €1,465.95

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CUTTING MECHANISM – SEWAGE

Pentair UFK MultiCut 08/2 ME

MultiCut blades for sewage through a thin pressure pipe.

€2,492.95

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Also check out the HOMA TP28 with 28 mm passage, or filter by impeller type in all submersible pumps.

Frequently Asked Questions

Which impeller is best for dirty water?

A vortex impeller. Solid parts largely flow past the impeller, so the pump rarely clogs. For toilet water through a thin pipe, choose a cutting mechanism.

What is the difference between a vortex and a channel impeller?

A channel impeller pushes all water through the blades and has higher efficiency, but clogs faster. A vortex impeller works with a vortex, is less efficient but much less sensitive to dirt.

When do I need a pump with a cutting mechanism?

If you need to pump toilet water or wastewater with solids through a thin pressure pipe, for example during a renovation or a long pipe route.

What does free passage mean?

The largest diameter of a solid part that can pass through the pump unhindered. The dirtier the water, the larger the free passage should be.