How to Fix a Boiler Making a Banging Noise (Kettling)

Overview

A boiler making a banging noise (kettling) can indicate limescale buildup. This guide covers diagnosing and fixing the issue.

Step-by-Step Fix

1. First, locate the pressure gauge on your boiler, which typically displays a needle or digital reading. The ideal pressure for a cold system usually falls between 1.0 and 1.5 bar; if it's too low, you may need to top up the system using the filling loop, or if it's too high, you might need to bleed a radiator to release pressure.
2. To address limescale, purchase a suitable domestic central heating system descaler from a DIY store or plumbing merchant. Carefully follow the manufacturer's instructions for introducing the descaler into your central heating system, which often involves adding it via a radiator or expansion tank, and allow it to circulate for the recommended duration before flushing.
3. Check if your central heating pump is running correctly by listening for a humming sound and feeling for vibrations when the heating is on. If the pump is silent or vibrating excessively, it may indicate a fault; ensure the power is off before carefully touching the pump, noting that a seized pump might require a professional.
4. Bleed your radiators to remove any trapped air that could be contributing to the banging noise. Using a radiator key, slowly open the bleed valve on each radiator, starting with the one furthest from the boiler, and close it immediately once water starts to trickle out and the hissing sound of air stops.
5. If the banging noise, or 'kettling,' continues even after trying these steps, it's crucial to contact a Gas Safe registered engineer immediately. A qualified professional can safely diagnose deeper issues, such as a faulty heat exchanger or persistent blockages, which require specialist tools and expertise to resolve.

Common Symptoms & Diagnostic Resolutions

Review the common error codes and operating symptoms below to quickly identify the root cause of the fault before ordering replacement parts.

Frequently Asked Questions