Central heating pump failure and pump seizure explained

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.

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.

Where we deal with this

• Winsley (BA15) · 9 mi
• Batheaston (BA1) · 10 mi
• South Stoke (BA2) · 8 mi
• Midsomer Norton (BA3) · 2 mi