Pump types
The short version: Most pumps are centrifugal, using a spinning impeller whose flow falls as lift rises, or positive displacement, moving a fixed volume each cycle.[1][2]
Two families
Most pumps are either centrifugal or positive displacement. A centrifugal pump converts rotational energy into flow: liquid enters the eye of a spinning impeller and is thrown outward into a diffuser or volute.[1] A positive-displacement pump traps a fixed volume and forces it out each stroke or turn.[2] The supplier’s 2026 guide compares the two for buyers.[3]
| Type | Principle | Behavior | Typical uses here |
|---|---|---|---|
| Centrifugal | Spinning impeller accelerates the liquid outward into a volute | Flow falls as head rises | Sump, effluent, sewage, most well pumps |
| Positive displacement | Traps a fixed volume and pushes it out each cycle | Nearly constant flow across pressures | Dosing, viscous fluids, some grinders (semi-PD) |
Summary from the general references.[1][2]
Centrifugal pumps
Centrifugal pumps are chosen for high flow, tolerance of abrasive liquids and simple construction, and are used for water, sewage and agriculture.[1] The first true centrifugal pump was built in the late 17th century by Denis Papin, and the curved vane was introduced by John Appold in 1851.[1] Their output depends on head: the higher the lift, the less they deliver, which is why pump curves matter when sizing a sump or sewage pump.[1][4]
Submersible, self-priming and dry-pit
A submersible pump has a sealed motor and sits in the liquid, which prevents cavitation and pushes liquid up rather than relying on suction.[5] A self-priming pump sits above the liquid and can clear air from its suction line. The supplier’s guides compare submersible with self-priming pumps and submersible with dry-pit wastewater pumps, in which the pump sits in a dry chamber next to the wet well for easier maintenance.[6][7]
Duplex and multiplex systems
In wastewater, a duplex system uses two pumps in one basin that alternate, so wear is shared and one can back up the other; quadplex systems use four.[8] The supplier’s blog post on duplex pump systems describes dual-cylinder pumping technology for industrial uses, which is a different, positive-displacement meaning of the word.[9] Buyers should check which sense a listing means.
Commercial sizing
For commercial and municipal lift stations, sizing works from peak inflow, static lift and friction losses in the force main to a design point on the pump curve, and then adds redundancy. The supplier’s seven-step guide covers this process.[10] The HOMA rail adapters in its catalog suit replacement pumps in existing stations.[11]
Terms
Head is the height, in feet, a pump can lift liquid; flow is measured in gallons per minute; cavitation is the formation and collapse of vapor bubbles at low pressure, which damages impellers.[1][5] More in the glossary.
Common questions
What is the difference between centrifugal and positive-displacement pumps?
A centrifugal pump throws liquid outward with an impeller and its flow falls as head rises; a positive-displacement pump moves a fixed volume each cycle.
Are sump pumps centrifugal?
Yes, nearly all are.
What is a dry-pit pump?
A wastewater pump installed in a dry chamber beside the wet well, rather than submerged.
Related entries
Endnotes
- ^ a b c d e f g Centrifugal pump. Wikipedia. Retrieved 9 November 2026.
- ^ a b c Pump (including positive-displacement pumps). Wikipedia. Retrieved 9 November 2026.
- ^ Centrifugal vs positive displacement pumps (2026). Pump Professionals (pumpprofessionals.com). Retrieved 9 November 2026.
- ^ What size sump pump do you need? Horsepower and GPM explained (2026). Pump Professionals (pumpprofessionals.com). Retrieved 9 November 2026.
- ^ a b Submersible pump. Wikipedia. Retrieved 9 November 2026.
- ^ Submersible pump vs self-priming pump (2026). Pump Professionals (pumpprofessionals.com). Retrieved 9 November 2026.
- ^ Submersible vs dry-pit wastewater pumps (2026). Pump Professionals (pumpprofessionals.com). Retrieved 9 November 2026.
- ^ Liberty Pumps (brand listing). Pump Professionals (pumpprofessionals.com). Retrieved 9 November 2026.
- ^ What is a duplex pump system? (2026). Pump Professionals (pumpprofessionals.com). Retrieved 9 November 2026.
- ^ How to size a wastewater pump for commercial or municipal applications (2026). Pump Professionals (pumpprofessionals.com). Retrieved 9 November 2026.
- ^ Homa grinder pumps & sewage pumps (brand listing). Pump Professionals (pumpprofessionals.com). Retrieved 9 November 2026.