Page 14 - Introduction

Don’t leave it to chance, get it right first time, if you think it’s expensive to hire a
professional wait to you count the costs of hiring a amateur.
Contact us on Skype/Phone: +44 (0) 161 8188974, Mobile: +44 (0) 7488298027,
email: paul.mcmullan@subtechengineers.com

Self-Priming Pumps
Most centrifual pumps need to operate with a flood suction as they require a minimum NPSH to be
able to operate correctly, if there is insufficent suction pressure you run the chance of the pump
cavitating.
In basic terms Sef-Priming pumps are designed with the suction inlet above the center line of the
impeller and a small suction chamber enableing them to evacuate any air in the suction a take a
suction lift.

With centrifugal self-priming pumps, the
Maximum suction lift is limited to
atmospheric pressure minus the
dynamic losses in the suction.
All require the suction line and pump
volute to be primed before the pump
is started. Its good practice on the
suction line to keep it as short as possible
and fit it with a foot valve if possible, to hold
the prime in the suction line and pump.

In addition to the small clean water self-priming pumps (above) there is a vast range of heavy duty
self-priming pumps for both clean and dirty water.

Some of the larger light commercial/industrial
Self-priming pumps can handle small soft
Suspended solids, the size depends on the
Size of the pump, this is the start of the
self-priming TRASH pump.

These large self-priming pumps
are commonly known as trash
pump as they are capable of
pumping dirty water with solids
content and sludge.

That’s what we do, we can help you with your design, selecting the right pump set for the right