---
title: "Centrifugal versus reciprocating pumps"
subject: "Hydro Power"
chapter: 7
key: "semester_6/hydro_power:centrifugal-vs-reciprocating"
source: https://www.bctengineer.com/q/semester_6/hydro_power/centrifugal-vs-reciprocating
site: BCT Engineering
---

# Centrifugal versus reciprocating pumps

Hydro Power · Chapter 7: Hydro-Electric Machines

- Asked in: 2079 Chaitra, 5 marks
- Video: [Difference Between Centrifugal and Reciprocating Pump](https://www.youtube.com/watch?v=85xOm0FIcdc) — BEST MECHANICAL ENGINEERING
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/hydro_power/centrifugal-vs-reciprocating
- Whole chapter: https://www.bctengineer.com/md/semester_6/hydro_power/chapter-7

## Question

Differentiate between Centrifugal and Reciprocating pumps.

## Short answer

Centrifugal pump: rotodynamic, large continuous discharge, low-medium head, needs priming, compact and low cost. Reciprocating pump: positive displacement, small pulsating discharge, high head, self-priming, large and expensive, handles only clean liquids.

## Answer

A **centrifugal pump** is a rotodynamic pump that raises the pressure of a liquid by the centrifugal action of a rotating impeller. A **reciprocating pump** is a positive-displacement pump in which a piston or plunger moving to and fro in a cylinder sucks in and pushes out a fixed volume of liquid per stroke.

| Basis | Centrifugal pump | Reciprocating pump |
|---|---|---|
| Working principle | Centrifugal force from a rotating impeller | Positive displacement by a piston |
| Discharge | Large, continuous and smooth | Small, pulsating (air vessels needed) |
| Head | Low to medium | High |
| Priming | Required before starting | Not required (self-priming) |
| Speed | High; can be coupled directly to a motor | Low; needs crank and gearing |
| Size and weight for same output | Small, compact, light | Large and heavy |
| Parts and maintenance | Few moving parts, easy maintenance | Many parts (valves, piston rings), more wear |
| Efficiency | Lower (about 60–80%) | Higher (about 85–90%) at its design point |
| Liquid handled | Can handle dirty, sandy or viscous liquids | Only clean liquids (valves get damaged) |
| Effect of closed delivery valve | Pressure rises only to shut-off head; safe for a short time | Pressure rises dangerously; needs a relief valve |
| Initial cost | Low | High |
| Uses | Water supply, irrigation, powerhouse drainage | Boiler feed, hydraulic presses, small high-head duties |

**Example:** a municipal water supply pumping 100 L/s against 40 m uses a centrifugal pump, while a boiler feed of 1 L/s against 300 m uses a reciprocating (plunger) pump.

In short, centrifugal pumps are preferred for large flows at moderate heads because they are cheap, compact and smooth running, while reciprocating pumps are used where a small flow is needed at a very high pressure.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the basic difference in working principle?
   A. Centrifugal is positive displacement; reciprocating is rotodynamic
   B. Both are positive displacement but with different valves
   C. Centrifugal is rotodynamic (centrifugal force of an impeller); reciprocating is positive displacement (piston)
   D. Centrifugal uses a piston; reciprocating uses an impeller
   Answer: C. Centrifugal pumps add energy through a rotating impeller; reciprocating pumps push a fixed volume per stroke. (Key point: Basic principle)

2. Which statement about priming is correct?
   A. A reciprocating pump needs priming; a centrifugal pump is self-priming
   B. Both need priming
   C. Neither needs priming
   D. A centrifugal pump needs priming before starting; a reciprocating pump is self-priming
   Answer: D. Air in a centrifugal pump prevents suction, whereas the reciprocating piston can displace air. (Key point: Priming and starting)

3. Compare discharge and head of the two pumps.
   A. Centrifugal gives large smooth discharge at low to medium head; reciprocating gives small pulsating discharge at high head
   B. Centrifugal gives small pulsating discharge at high head; reciprocating gives large smooth discharge
   C. Both give large discharge at very high head
   D. Centrifugal gives high head and pulsating flow
   Answer: A. That is why centrifugal pumps suit water supply and reciprocating pumps suit boiler feed. (Key point: Discharge and head)

4. What happens if the delivery valve is closed while running?
   A. Centrifugal pressure rises dangerously; reciprocating is safe
   B. Centrifugal pressure rises only to shut-off head (safe briefly); reciprocating pressure rises dangerously and needs a relief valve
   C. Both are safe indefinitely
   D. Neither pressure changes
   Answer: B. Positive displacement keeps pushing fluid, so pressure keeps rising unless relieved. (Key point: Closed delivery valve)

## Related in Hydro Power

- [Working principle of centrifugal and reciprocating pumps](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Acentrifugal-reciprocating-working) — Hydro Power, chapter 7

## Related in other subjects

- [Pumps in series and parallel on a system](https://www.bctengineer.com/question.md?key=semester_5%2Ffluid_machines%3Apumps-series-parallel-numerical) — Fluid Machines, chapter 4