Pumps and Systems

What Is a Jet Pump? Working Principle, Specifications and Applications

Thanks to their built-in ejector, jet pumps can expel air from the suction line and draw water from shallow wells and tanks by themselves. Learn how they work and their key specifications.

ORFA Technical TeamUpdated: Oct 30, 20263 min read

Jet pump – self-priming water pump with ejector

For shallow wells, tanks and cisterns where the pump is installed above the water level, one of the most practical solutions is the jet pump. A jet pump is self-priming thanks to an ejector integrated into its casing: it evacuates the air in the suction line and can lift water from a depth of up to about 9 metres.

This article summarises how jet pumps work, their technical data, the materials used and the applications they suit.

How Does a Jet Pump Work?

A jet pump consists of a centrifugal impeller and an ejector (nozzle and venturi/diffuser) placed in front of it. Part of the water delivered by the impeller is routed back to the nozzle. Water leaving the nozzle at high velocity creates a low-pressure zone around it, which draws water and air from the suction line. After the initial fill, the pump therefore evacuates the air in the suction line by itself and starts drawing water.

The ejector improves suction performance, but because it continuously recirculates part of the water, jet pumps have lower hydraulic efficiency than standard centrifugal pumps. In return, they are more tolerant of air in the suction.

Technical Data

Feature	Range
Motor power	Typically about 0.37 kW (0.5 HP) – 2.2 kW (3 HP), depending on model
Flow	Depends on model; up to about 160 l/min (9.6 m³/h) for larger models
Head	Depends on model; up to about 95 m (approx. 9.3 bar) for larger models
Suction lift	Max. 9 metres

These values show the general range of the product line; check each model’s performance on its own curve. The maximum suction lift applies to clean, cold water at sea level with a leak-tight suction line. Higher water temperature, altitude and suction line losses reduce the achievable suction lift.

Materials

Casing: Cast iron or stainless steel
Motor winding: 100 percent copper
Shaft and impeller: Stainless steel or bronze

Benefits

Self-priming: After the initial fill it evacuates the air in the suction line by itself.
Compact and practical: Easy to install in small spaces and simple to maintain.
Corrosion resistance: Stainless steel models last long in humid environments.
Suitable for booster use: Can be combined with a pressure tank and pressure switch in small water pressure systems.

Applications

Domestic water supply from shallow wells, tanks and cisterns
Garden and small-scale agricultural irrigation
Water pressure boosting for detached houses and small businesses
Clean water transfer

Jet pumps are designed for clean water. Sand, mud or solids clog the ejector nozzle and wear the impeller; for chemical and aggressive liquids or wastewater, choose pumps designed for those duties. For wells where the water level is deeper than 9 metres, use submersible pumps.

Tip: Fit a foot valve with strainer at the end of the suction line and make sure the line rises continuously towards the pump. The suction line then stays full when the pump stops, so air does not have to be evacuated at every start.

Frequently Asked Questions

How deep can a jet pump draw water from?

With clean, cold water and a leak-tight suction line, it can lift water from a maximum depth of about 9 metres. This value falls as the suction line gets longer and as water temperature and altitude increase.

Does a jet pump need to be filled before the first start?

Yes. Although it is self-priming, the pump casing must be filled with water through the priming plug before the first start. Never run the pump dry.

Is a jet pump suitable for sandy water?

No. Sand and solids clog the ejector nozzle and wear the impeller. Choose a pump type suitable for sandy water instead.

Conclusion

With their self-priming design, compact size and easy installation, jet pumps are a practical solution for clean water supply from shallow wells and tanks, irrigation and small-scale pressure boosting. Choosing the right model and using it with clean water ensure a long service life. Browse the models in our Jet Pumps product group.

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