Important pump terms & abbreviations

Pump Curve

Every centrifugal pump has its own so-called pump curve. Think of it as the pump’s fingerprint: a graph showing how much pressure (head) the pump delivers at a given capacity. The vertical axis represents the head, while the horizontal axis shows the capacity in m³/h or l/min.

This curve helps you choose the right pump for your task. Note: manufacturers usually test with water. Other fluids can affect the curve, so always check whether the pump is suitable for your specific application.

Pump Capacity (Q)

Pump capacity simply refers to how much water flows through the pump per hour or per minute. Usually expressed in m³/h (cubic meters per hour) or l/min (liters per minute). Don’t have a flow meter on hand? No worries, use our easy capacity calculator.

Pump Head (H)

The pump head indicates how far (in vertical meters) a pump can push water upward — for example, from a ditch to a spray boom or from a basement to street level. It’s often indicated as mwc (meters water column). A common term here is TDH, which stands for Total Dynamic Head. That’s the combination of elevation difference and resistance in your piping — the total, in other words. To measure the total head of your system, you can use a pressure gauge and vacuum gauge.

Pump Power (P)

Pump power indicates how much energy your pump consumes and is expressed in kilowatts (kW). This is also known as input power or shaft power. It is specified in the pump curve or pump specifications. A high-efficiency pump consumes less energy. So always pay attention to the pump efficiency (η) and choose an operating point as close as possible to the BEP.

Pump Efficiency

Pump efficiency reflects how effectively a pump operates. In other words: how much of the input energy is actually used to move water. The higher the efficiency, the less energy is lost — and you’ll notice that in your energy bills and pump lifespan.

A pump with good efficiency runs smoother, quieter, and wears out more slowly. It also means you can achieve the same results with less power. If you choose a pump that doesn’t fit your application, it will operate outside its ideal range. That results in unnecessary energy use and increased maintenance.

BEP of a Pump

BEP stands for Best Efficiency Point: the point at which a pump runs most efficiently. If your operating point is close to this, you’ll have a reliable pump that uses less energy, runs more quietly, and requires less maintenance. That makes both you and your wallet happy. If you’re too far from the BEP, problems often arise such as noise, overheating, or even damage to the impeller or bearings.

NPSH

NPSH stands for Net Positive Suction Head. Sounds technical, but it basically comes down to the pressure on the suction side of the pump — and that’s more important than you might think.

There are two forms of NPSH to distinguish:
NPSHa is the pressure currently available in the system. It’s determined by the height of the liquid column, temperature, vapor pressure of the fluid, and piping resistance.
NPSHr is the minimum pressure the pump needs to function properly. This value is specified by the manufacturer and can be found in the pump curve.

Why is the difference important? Because determining the correct NPSH makes the difference between a properly functioning pump and one that’s slowly destroying itself. If the available pressure (NPSHa) is lower than what the pump requires (NPSHr), vapor bubbles will form in the liquid. These bubbles later collapse — a process called cavitation — and that causes damage to the impeller and other components.

Cavitation is a silent killer. You usually only hear it when it’s too late: a rattling noise, vibrations, or a pump that suddenly performs worse. In the worst case, the entire pump must be overhauled or replaced.

That’s why, when selecting a pump, it’s crucial that NPSHa is always higher than NPSHr, preferably with a margin. Especially when working with hot liquids or long suction lines, things can get critical quickly.

Piping Resistance

As soon as water flows through a pipe, hose, or line, resistance occurs. This is due to friction between the fluid and the inner wall of the pipe. The faster and farther the water needs to go, the more resistance you get. And the more resistance, the harder your pump has to work.

Piping resistance is therefore a key factor in selecting the right pump. It directly affects the required head and energy consumption. A pump may look fine on paper, but if you didn’t account for piping resistance, it could severely underperform in practice.

Several factors influence resistance:

• The length of your piping: the longer the pipe, the more friction.
• The diameter of the pipe: the narrower, the more pressure loss.
• The material and layout of the piping: sharp bends, rough inner walls, or narrowings make things harder for the pump.
• And not to forget: the speed at which water flows through the pipe — your pump capacity, in other words.

In short: piping resistance is not something to ignore. It’s a serious factor that can make or break your installation.

Solids Passage

The solids passage of a pump indicates the maximum size of solid particles that can pass through the pump without causing problems, expressed in millimeters (mm). Think sand, sludge, leaves, or other coarse material that may be present in the water.

A larger solids passage means the pump is more suitable for dirty or contaminated water. Pumps with a small solids passage are not equipped for this and can easily clog or get damaged.

Common Units

When talking about pumps and moving water, various units are used. Below are some commonly used ones: