Central heating pump failure and pump seizure explained
The pump is what moves hot water around the system after the boiler heats it. When it fails, the burner can still fire perfectly and still trip out on overheat within minutes.
What we check first with a failed or seized circulating pump
Pumps seize most often after standing idle over a long summer, when accumulated sludge or scale locks the impeller in place. A pump that hums but does not turn is usually seized rather than electrically dead; one that is silent has likely lost power or failed internally. Bearing wear causes a grinding or whining noise that gets worse over weeks before the pump stops altogether.
Published business details
- Based at 24 Bristol Road, Radstock, BA3 3EE
- Telephone enquiries: 07516 118198
- Opening hours: Monday to Friday, 8:30am to 5:00pm
A failed or seized circulating pump: engineer's shortlist
- A humming, non-turning pump usually means a seized impeller
- Freeing a seized shaft with a screwdriver in the rear vent screw sometimes restarts it
- Persistent seizing points to sludge contamination needing a flush
- A silent pump suggests an electrical or PCB-driven fault
- Modern pumps are usually replaced as a sealed unit rather than repaired
Questions we get asked
- Can a seized pump be freed without replacing it?
- Sometimes, briefly, but a pump that has seized once is likely to seize again unless the underlying sludge contamination is also addressed.
- Is pump replacement a big job?
- No — most modern circulating pumps are replaced in under an hour once isolated, though older systems occasionally need draining down first.
Related help pages
- Efficiency controlsLoad compensation: how a modern boiler reads your room temperature
- Symptom guideHeating fine but hot water only lukewarm: what causes the split
- Cylinder heatingCylinder immersion heater faults and when to use one as backup
- Cold-weather faultsCondensate pipework design and why freezing keeps recurring
- Overheat lockoutWorcester E9 overheat fault: why the boiler cut out hot
- Noise diagnosisHumming or vibrating pump: noise diagnosis on a heating system
Services that cover this
Where we deal with this
Sorted quickly: a failed or seized circulating pump
In practice: A pump fault often masquerades as an overheat lockout, so checking whether the pump is actually turning is one of the first things worth doing.
Jamie Crawford Heating is based at 24 Bristol Road, Radstock, BA3 3EE.
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