Water Pump Terminology


Manual or Automatic Pumps

Manual: a float switch is not fitted. The pump requires an operator to control the pump by switching it off or on at the mains.

Auto: a float switch is fitted. The pump will turn itself on and off automatically as the water level rises and falls. The float switch must be actuated for the pump to operate. The pump is automatically controlled by a level switch.

If an automatic pump is desired, you must ensure the sump is large enough to allow free movement of the float switch. For more information on the types of automatic float switches, please visit our automatic float switch blog.

Pump Connections

If the figure is given an imperial measurement (e.g. 1¼”) then the inlet and/or outlet is threaded and a hose tail is required as an extra to fit a flexible pipe.

If the figure is give a metric measurement (e.g. 32mm) then the inlet and/or outlet is supplied with a hose tail to enable fitting to a flexible pipe.

Outlet: this is the internal diameter size of the discharge pipe. If you need to reduce the outlet size, it is worth noting that there will be increased friction losses, and pumping capacity will be reduced. The risk of blockage is also increased.

Inlet: this is the internal diameter size of the inlet pipe. This should not be reduced.

Power

Voltage: the voltage that this model is available in. When you see two voltages on one line e.g. 110•230 this means the pump is available in one or the other voltage, but not dual voltage.

Amp: this is the full load current specified on the motor rating plate, i.e. the running current. Instantaneous starting currents will be several times this figure and details can be supplied if needed for any application, e.g. when running off a generator.

Current: the single and three phase pumps run on A.C. (alternating current) while low voltage pumps run on D.C. (direct current).

Frequency: all our AC motors are designed for 50Hz operation.

Pump Dimensions & Weights

W x L x H: (width x length x height) or “diam x h” (diameter x height): the figures published are either taken from the manufacturer’s specifications or our measurements. If your application needs precise information we recommend that you request written confirmation from our Sales Department.

Dry Weight: is the weight of the pump, excluding any power cable, connections or hoses. For Tsurumi free-standing sewage pumps, it includes the flanged elbow.

Packing Weight: is the weight of the pump when delivered, including all packaging.

NB: figures published are approximate. The data should only be used as a guide. We recommend asking for written confirmation if you require specific information.

Pumping Performance

Flow: flows are given in litres per minute and are based on pumping clean, cold water (or diesel, or oil, when referring to fuel and lubricant pumps), through the outlet bore specified.

Head: The figure is the maximum height of a vertical column of water that the pump could support if there were no other losses in the system.

Suction Lift: A ‘suction lift’ is the distance from the pump’s centre line to the water level. There are few limitations on the discharge side of a pump, but there are many on the suction side. We recommend that submersible pumps are chosen in preference to surface mounted pumps where possible.

Performance Curves: these indicate the output possible at measured points. Care should be taken not to select a pump for operation off the bottom or the top of the curve, as this could lead to early pump failure.

Motor enclosure ratings: motors are classified by the degree of enclosure protection. The rating consists of the letters “IP” followed by two characteristic numerals.

The first numeral (0 – 6) designates the degree of protection against contact with live or moving parts inside the enclosure and protection of machines against ingress of solid foreign bodies.

The second numeral (0 – 8) designates the degrees of protection of machines against harmful ingress of liquids.

Solids Handling

Free Passage: this is the size of the solids that the manufacturer specifies that the pump can pass.

Water Pump Engines

Petrol driven pumps run on unleaded fuel.

Diesel engine pumps run on red or white diesel, but not bio-diesel.

Oil Alert: this is a protection device for petrol engines that will stop the engine during operation or prevent the engine starting if there is insufficient oil.

Centrifugal Pumps:

95% of our water pumps are centrifugal pumps. Pumps do not ‘suck’, instead these pumps create a pressure difference due to a centrifugal force, which draws water into the pump.

Inside the pump, a motor will spin at high speed, with an impeller attached to the end of it.

As the impeller spins, it creates a centrifugal force and as a result a pressure difference occurs. This pressure difference draws water in through the inlet of the pump and pushes it out of the outlet under pressure (which is connected to a pipe).

Air and water do not have the same characteristics which is why centrifugal pumps cannot prime automatically. Our centrifugal engine driven pumps are however ‘self-priming’. They require water in the casing to enable them to pump. Typically, submersible pumps do not require any priming as they are submersed in the water.

Diaphragm Pumps:

Diaphragm pumps are much less common than centrifugal pumps, and as a result we only sell 2. The DryMax Engine Driven Trash Diaphragm Pump and the TD Petrol Trash Automatic Priming Diaphragm Pump.

Diaphragm pumps use a reciprocating vane on either side of a diaphragm to pump a liquid.

Diaphragm pumps have good dry running capabilities and prime automatically, however, they are much more expensive than centrifugal pumps.

PLEASE NOTE

The data provided should only be used as a guide. We make every effort to ensure information is accurate, however we cannot be held responsible for any loss suffered as a result of errors, or approximations. Our pump range is continually being updated and we reserve the right to alter specifications without notice. If your application requires more specific information we strongly recommend you contact our sales department for written confirmation.