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Why has my pump lost suction?

In our experience as a pump supplier and repairs provider, one of the most common causes of pump failure is a loss of suction. Here we look at a few of the reasons for suction loss and what can be done about it.

Does your pump need to be primed?

Put simply, pumps cannot move air or vapour so need an initial water feed to operate. Submersible pumps do not apply, as by their nature they are immersed in the liquid being pumped, however surface-mounted pumps must be primed before activation. Allowing a pump to run un-primed for extended periods will eventually cause it to overheat and may cause the impeller to seize.

Is the pump air locked?

If you’re certain the pump is primed, try starting and stopping it a few times. If the pump begins to work, it’s likely that there was an air lock at some point in the system.

Check for blockages

A pump’s suction pipe can be prone to clogging up by mud, leaves or other debris, while filters should be routinely checked and cleaned.

Could it be cavitation?

Cavitation occurs when bubbles or voids form in a liquid being pumped. When the blades of the pump’s impeller pass through the liquid, low-pressure areas are formed. As the impeller accelerates, the pressure continues to drop and the fluid vaporises, forming small bubbles. When these bubbles collapse in a higher-pressure part of the pump, shock waves are created which make a loud rumbling or cracking noise. Over time, these shock waves cause damage to the pump’s impeller and eventually lead to failure. To avoid cavitation, reduce the motor’s rpm or use a double suction impeller if possible.

If you’re still stuck, why not contact our pump repairs workshop? Our experienced team of engineers have the expertise to diagnose and correct pump problems, making your equipment efficient and smooth-running once again.

For all pump sales and repairs enquiries, call Matthew Gibbons on 07970 676272 or email

Pumps & Controls

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