Banging, gurgling, kettling: heating noises explained

Heating systems are rarely silent, but the type of noise is diagnostic. Here's what the common ones mean, roughly in order of how urgently they deserve attention.

Kettling: a rumble or whistle like a kettle

Scale or sludge on the boiler's heat exchanger makes water boil where it shouldn't. It stresses the exchanger — the most expensive part of the boiler — so this one is worth acting on. The fix is usually a chemical cleanse and, in harder water, treatment to stop it recurring.

Banging or knocking pipes

A single bang when heating starts is usually thermal expansion — pipes moving against joists as they warm. Annoying but harmless; securing the pipe or adding a felt pad where it rubs cures it. Rapid hammering when taps close is water hammer, which a fitted arrestor or adjusted valve resolves.

Gurgling radiators

Air in the system. Bleed the radiators (our guide covers it) and re-pressurise the boiler afterwards. If gurgling returns within weeks, air is being drawn in somewhere — that's a system fault worth finding.

Humming or droning

Often the circulation pump running faster than the system needs, or a pump on its way out. A speed adjustment is a five-minute job; a failing pump is better replaced before it fails in January.