Starting out in the world of pumps? Welcome to the deep end. Whether you’re designing systems, troubleshooting equipment, or just trying to sound like you know what you’re talking about in a plant meeting, these 10 terms will keep you out of trouble (and maybe even impress your boss).
No jargon overload here—just clear definitions and real-world context.
1. Flow Rate
Let’s start simple. Flow rate is how much fluid a pump moves over time, usually measured in litres per minute (L/min) or cubic metres per hour (m³/h). Use our flow rate converter tool.
Why it matters: It tells you if the pump can move enough fluid to meet your process demands.
Watch out for: Confusing flow rate with velocity—they’re related but not the same thing.
2. Head
Head is the height the pump can raise fluid. It’s usually measured in metres and represents energy, not just vertical lift.
Think of it like: The pressure a pump creates, expressed as an equivalent height of liquid.
Total Dynamic Head (TDH) is the total resistance the pump must overcome—including elevation, friction losses, and pressure.
3. NPSH (Net Positive Suction Head)
A little intimidating at first, but crucial. There are two types:
- NPSHa (Available): What your system provides
- NPSHr (Required): What your pump needs to avoid cavitation
Why it matters: If NPSHa is less than NPSHr, your pump will cavitate—causing noise, vibration, and eventually failure.
Golden rule: NPSHa > NPSHr, always.
4. Cavitation
This is the sound of your pump crying for help. Cavitation happens when vapor bubbles form in low-pressure areas and then collapse violently. It’s bad news.
What it sounds like: Gravel rattling around inside your pump.
Causes: Low NPSH, high suction lift, clogged filters, or running too far off the curve.
5. Best Efficiency Point (BEP)
Every pump has a sweet spot where it runs smoothly, quietly, and efficiently. That’s the BEP.
Why it matters: Operating too far left or right of this point leads to energy waste, seal wear, and vibration.
Pro tip: Size your system to run as close to BEP as possible.
6. Viscosity
A fancy word for how “thick” a fluid is. Water has low viscosity. Honey? Very high.
Why it matters: Viscous fluids need more power to move. They also change how pumps behave—especially centrifugal ones.
Rule of thumb: High-viscosity? Consider a positive displacement pump.
7. Impeller
The rotating component that does the actual work inside a centrifugal pump. It slings fluid outward to create velocity and pressure.
Types: Open, semi-open, enclosed. Each has pros and cons depending on solids, efficiency, and maintenance.
8. Positive Displacement (PD) Pump
Unlike centrifugal pumps that rely on velocity, PD pumps trap and push fluid. Think gear, diaphragm, peristaltic, and lobe pumps.
When to use them: For thick fluids, precise dosing, or when flow needs to stay consistent despite pressure changes.
9. Self-Priming
A self-priming pump can clear air from the suction line and start pumping without external help.
Why it matters: Useful in systems where the pump sits above the fluid or where air is common (like dewatering or wastewater).
Don’t assume all pumps self-prime—many don’t.
10. Shutoff Head
This is the maximum head a centrifugal pump can produce with zero flow—basically when the discharge valve is closed.
Why you should care: It’s a good design limit and safety check. Running against a closed valve too long can overheat the pump and cause damage.
Knowing these ten terms won’t make you a pump expert overnight—but it’ll give you a solid footing. From selecting the right unit to spotting early signs of trouble, this stuff is the foundation of real-world engineering.
Pumps aren’t just “black box” components—they’re dynamic, mechanical systems that behave in very predictable (and sometimes unpredictable) ways. Learn the language, and you’ll be a step ahead.
View a full list of pump terms here.
