Glossary – Pump Terminology

Activated Carbon

Used to reduce organic compounds in water.

Anti-Blocking System

Brief periodic activation of pumps, solenoids or motorised valves to prevent either jamming of pump shafts due to lubricant settlement and valves due to limescale, corrosion or contaminants.


A term not used in this catalogue but often used in Europe to denote automatic operation of pressure controllers and automatic pumps.

Automatic Pump

Automatic pumps contain their own electronic control system designed to shut off the pump when a tap or outlet valve is closed and restart it when opened. They can be left permanently energised, and will pump only when water is required. The control system senses both pressure and flow to control it’s operation.

BMS Output

An output provided on a control system which integrates with a Building Management System. BMS outputs may be in the form of a closing contact, or a data connection providing advanced functionality.

Centrifugal Pump

The majority of pumps used for moving water in domestic and commercial buildings are centrifugal, consisting of an induction motor whose rotor shaft is directly fixed to an impeller. Water enters the centre of the impeller and is thrown outwards by shaped vanes causing fluid to exit the pump under flow and pressure. Suction is then created at the inlet by evacuation.


Capacitor (Alternative word).


A static (non-moving) plate containing steeply angled vanes surrounding the impeller of a pump, altering the flow of water to create increased pressure. The majority of general purpose and pressure boosting centrifugal pumps contain a diffuser.

Duty Assist

An arrangement of 2 or more pumps in which pumps are set to start at different pressures, to enable both pumps to work together when a substantial demand for water (drop in pressure) is detected. Duty Assist systems usually operate a Duty Standby function as well.

Duty Standby

An arrangement of 2 or more pumps in which only one pump at a time is used. The pump used may alternate by start-up or by timing. In the event of a pump failure the failed pump is isloated and the duty changes over to the remaining pump(s).

Flexible Impeller

An impeller made of soft material, usually NBR or silicone, which is composed of flexible fins  and is mounted eccentrically within a circular housing, compression of the fins on the outlet side reduces each cavity and forces water through the pump.

Floating Intake

A short length of intake hose with a strainer and float ball mounted at the far end to suspend the strainer just beneath the surface of the water. A normal fitment in rainwater installations to minimise the intake of debris.

Float Switch

An electrical switch which floats on the end of a cable and switches depending on its angle. Often found on drainage pumps to produce automatic operation.

Gear Pump

A type of progressive cavity pump consisting of 2 intermeshed gear wheels enclosed in a housing with fine clearance around the gears. As the gears contra-rotate, fluid is carried around the outside edge. These are suited to viscous fluids such as heavy oils.


A feature of a pump installation whose design facilitates the isolation and safe replacement of a pump while the system remains powered and operating, removing the need to shut down the pump set.


European terminology for Stainless Steel, as in “Inoxidisable”.

IP Rating

A standard rating for devices specifying ingress protection from dirt, water and objects. The first digit denotes protection from dirt and solid objects, the second digit is the protection against water entry. A full chart of IP ratings is shown at the end of this catalogue.

Jet Pump

A jet pump is a centrifugal impeller/diffuser pump which includes a venturi situated within the inlet. Some of the pumped water is recirculated and passes through the venturi at high velocity, creating increased suction. Jet pumps are well suited to surface mounting above a well or water tank.

Leak Detection

Monitoring of the startup intervals of a pump to determine the likely prescence of a leak and to effect a   subsequent shutdown of the pump, if necessary.


Pressure Gauge (Alternative word)


A water dosing medium which reduces the tendency of water to form limescale deposits.

Pressure Vessel/Expansion Vessel

A steel cylinder with a water connection at one end, an air valve at the other, and a flexible membrane in between. When pre-charged with compressed gas the membrane fills the tank, and compresses a side when water enters under pressure from the water inlet. Used with pressure based pump controllers and automatic pumps to store pressurized water, increasing efficiency, prolonging pump life, and providing smoother and more precise operation.

Progressive Cavity

Pumps that do not rely on centrifugal action, but the use of one or more cavities which are progressed from inlet to outlet. Pressure is not related to shaft rotation speed and so the usual pump affinity laws do not apply, they can operate effectively at very low speed without loss of pressure. Common technologies include flexible impeller, screw, vane, gear, piston, swash plate, and diaphragm.

Self Priming

Refers to pumps which are designed so as to automatically evacuate air when submerged and so can be started without seperately filling with water. Self priming pumps which can be used surface mounted usually need priming in this configuration and have a suitable filling port. Self priming depends on the outlet being sufficiently open to allow air movement, and also may be inhibited by floating intakes with attached non-return valves. Self priming does not mean an empty pump will suck water up through the inlet hose, installations of that type will still need to be initially primed.

Single/Multi Stage

Single stage pumps contain a single impeller/diffuser set, Multi stage pumps contain several, each set being a Stage, with the flow exiting the diffuser of one stage and passing into the centre of the impeller of the next stage. Multi stage pumps have increased performance.

Single/Multipoint Pressure Control

Basic pressure control switches on at a fixed pressure and switches off by flow sensing. By this method it can reach maximum pump pressure regardless of the characteristics of the pump. Most multi-purpose consumer pressure controllers work in this way. Multi-point pressure controllers are programmed with a start and stop pressure to suit the performance curve of the pump, resulting in much higher efficiency.


Plastic (often polypropylene) mechanically strengthened with fibres. Very strong and able to be moulded precisely. Used to create cost-effective parts where cast metals would otherwise be needed.


Non-return valve, a.k.a. Backflow valve. Allows water to flow in one direction only, essential to the operation of all automatic pumps and most pressure based control systems based on centrifugal pumps.


A pump inlet component into which a small amount of the pumped water is recirculated, entering in the direction of flow at high velocity creating a venturi effect (suction). Pumps with a venturi are also often known as Jet Pumps.

VFD/VSD/Inverter Drives

A type of multi-point pressure control which varies the speed of the motor by re-inverting the power supply at varying speeds. Variable speed pump controllers provide high efficiency as well as a soft-start function. Losses are incurred by power conversion making these solutions less efficient than other methods at full speed, particular attention should be given to correct sizing of the pump.