Choosing a pump starts with understanding the system—not choosing a pump catalogue.
A pump can only perform as intended if it matches the application’s hydraulic requirements, the fluid being pumped and the operating conditions. Missing or incorrect information often leads to oversized pumps, undersized pumps, excessive energy use, seal failures, cavitation and reduced equipment life.
Before comparing pump types or manufacturers, gather the information below. These are the questions every pump engineer should answer before selecting a pump.
Start with the required duty point
Every pump selection begins with the required duty point. The duty point is the combination of flow rate and total head where the pump is expected to operate.
Without these two values, meaningful pump selection is impossible.
You need to know:
- Required flow rate (L/s or m³/h)
- Total dynamic head (m)
- Whether these values are constant or vary during operation
The pump curve must intersect the system curve as close as practical to the required duty point. Selecting a pump before defining the duty point usually results in unnecessary compromises.
Understand the fluid being pumped
A pump moves fluids, but not all fluids behave the same way.
The fluid’s physical properties determine which pump types, materials and sealing arrangements are suitable.
Typical information includes:
| Property | Why it matters |
|---|---|
| Fluid name | Identifies compatibility issues |
| Temperature | Affects viscosity, materials and seal selection |
| Density | Influences power requirements |
| Viscosity | Changes pump performance and efficiency |
| Solids content | Determines wear and pump design |
| Particle size | Affects impeller clearance and passage size |
| Corrosiveness | Determines suitable materials |
| Abrasiveness | Influences wear resistance |
| Hazard classification | May require specialised sealing or compliance |
Even a small change in fluid properties can significantly affect pump performance.
Determine the available suction conditions
Many pump problems originate on the suction side rather than the discharge side.
Understanding the available suction conditions helps prevent cavitation, which occurs when local pressure falls below the fluid’s vapour pressure and vapour bubbles form inside the pump.
Information to collect includes:
- Static suction head or suction lift
- Suction pipe length and diameter
- Number of fittings and valves
- Fluid temperature
- Tank operating pressure
- Site elevation where relevant
This information allows calculation of the available Net Positive Suction Head (NPSH), which must exceed the pump’s required NPSH with an appropriate safety margin.
Understand the pipe system
The pump does not operate in isolation. It operates as part of a complete pipe system.
Changes in pipe size, elevation or fittings alter system resistance and therefore change the operating point.
Useful information includes:
- Pipe diameters
- Pipe lengths
- Pipe material
- Elevation differences
- Number and type of valves
- Number of elbows and fittings
- Filters, heat exchangers or other equipment in the flow path
These details determine the system curve, which is essential for selecting an appropriate pump.
Define how the pump will operate
The operating profile often has as much influence on pump selection as the hydraulic duty.
Consider questions such as:
- Will the pump run continuously or intermittently?
- Does the flow rate change during operation?
- Will a Variable Frequency Drive (VFD) be used?
- Is standby capacity required?
- Will multiple pumps operate in parallel or in series?
- How many starts per hour are expected?
A pump selected for continuous operation may not be suitable for frequent stop-start duty.
Consider the installation environment
The installation location affects both reliability and maintenance.
Important factors include:
- Indoor or outdoor installation
- Ambient temperature
- Flood risk
- Dust or corrosive atmosphere
- Hazardous area classification
- Available power supply
- Space for maintenance
- Lifting access
Ignoring installation constraints can make routine maintenance unnecessarily difficult or increase installation costs.
Understand maintenance and reliability requirements
Different applications place different priorities on maintenance.
For some systems, the lowest purchase price may be appropriate. For others, reliability and ease of maintenance are far more valuable than initial cost.
Questions to consider include:
- What level of reliability is required?
- What are the consequences of pump failure?
- Is downtime acceptable?
- Are maintenance staff available on site?
- Are spare pumps installed?
- Are spare parts readily available?
These factors influence pump design, sealing arrangement and maintenance strategy.
Regulatory and compliance requirements
Some applications must comply with specific industry standards or regulatory requirements.
Examples include:
- Drinking water systems
- Food and beverage processing
- Pharmaceutical production
- Hazardous chemicals
- Mining operations
- Fire protection systems
These requirements may determine acceptable materials, testing standards or installation methods before the hydraulic selection even begins.
A practical pump selection checklist
Before selecting a pump, collect the following information.
| Information required | Typical units or description |
|---|---|
| Required flow rate | L/s or m³/h |
| Total dynamic head | m |
| Fluid type | Water, slurry, chemical, oil etc. |
| Temperature | °C |
| Density | kg/m³ |
| Viscosity | cP or mm²/s |
| Solids concentration | % or description |
| Particle size | mm |
| Suction conditions | Head or lift |
| Pipe sizes and lengths | mm and m |
| Operating profile | Continuous, batch or variable |
| Power supply | Voltage and frequency |
| Installation environment | Indoor, outdoor, hazardous area |
| Maintenance expectations | Criticality and service intervals |
Collecting this information before reviewing pump curves saves time and greatly increases the chance of selecting the correct pump the first time.
The right pump starts with the right information
Most pump selection problems begin long before anyone looks at a pump curve. They begin with incomplete system information.
A clear understanding of the duty point, the fluid, the pipe system and the operating conditions allows pump options to be evaluated on technical merit rather than guesswork.
If some of this information is unknown, the next step is to calculate or measure it before selecting a pump. A well-defined application almost always leads to a better pump selection.
About The Pump Expert
The Pump Expert provides independent, practical education for engineers, maintenance teams and pump users. Our content explains how pump systems work, why problems occur and how better engineering decisions improve reliability, efficiency and operating life.
Can I select a pump using only the required flow rate?
No. Flow rate alone is not enough. You also need the total dynamic head, fluid properties and operating conditions to identify a suitable pump.
What is the most commonly overlooked piece of information?
Total dynamic head is frequently estimated rather than calculated. An inaccurate head calculation often results in selecting the wrong pump.
Why does fluid viscosity matter?
Viscosity changes pump performance, efficiency and power consumption. Pumps handling viscous fluids may perform very differently from their published water performance curves.
What happens if the pump is oversized?
An oversized pump may operate away from its Best Efficiency Point (BEP), increasing energy consumption, vibration, seal wear and maintenance costs.
Can the same pump handle different fluids?
Sometimes, but not always. Changes in viscosity, solids content, corrosiveness or temperature may require different materials, seals or even a different pump type.
Last Updated on July 27, 2026 by TPE