Water Pump Selection Information

A. Identify the liquid to be pumped:-

i) Is it potable water?
Aluminium pumps will contaminate. All Atalanta pumps other than the Gannet D75 and 100 are safe with drinking water.

ii) Is it salt water?
Aluminium pumps will corrode.

iii) Does it contain solids?
All pumps have a maximum solids capacity. Atalanta models have generous solids handling tolerance (check individual data sheets for exact details). Note: The Gannet range has been specially developed for “Trash” pumping.

B. Determine the suction lift required.

This figure is usually measured in metres and is the height difference between the water source and the pump inlet, together with any friction caused by the length, size and material of pipe or fittings used:

At sea level maximum practical static lift of a pump is 7.5m. At 1,500m AMSL (above mean sea level) it drops to around 5.7m. For best efficiency the pump should always be located as close as possible to the water source.

C. Determine the delivery head required.

This figure is usually measured in metres and is the height difference between the pump outlet and the delivery point, together with any friction losses caused by the length, size and material of pipe(s) or fittings used.

D. Identify site conditions.

The performance of petrol and diesel engines is considerably affected by altitude and to a lesser extent by ambient temperature (humidity).

i) For every 500m AMSL the power of the engine, hence pump performance, is derated by approximately 6%

ii) For every 5°C above 25°C the power of the engine is derated by approximately 2.5%.

iii) Add the figures from i and ii together to get overall reduction in pump performance. Example: A pump that is capable of producing 50m³/hour at 20m total head when operating at sea level at 20°C ambient will only produce 42.75m³/hour when operating at 1,000m AMSL at 30°C ambient temperature conditions.

E. Having taken all the above factors into account you can now determine the total head required (i.e. delivery head plus suction lift).

The graphs shown on Atalanta pump data sheets is total head at maximum recommended operating speed. For best efficiency select on or slightly left of the curve. Note: Output of the pump is a function of speed. Reduction of engine speed may enable adjustment to meet system demand.

If required we can provide:-
Graphs of pump performance at various speeds and engine derating charts for altitude, temperature and humidity.

If in doubt, please click here to contact our technical department.