Water hammer: the sharp bang that follows a valve closing

Things worth knowing about water hammer in pipework

• Water hammer is a single sharp bang timed to a valve closing, not gradual noise
• Fast-closing motorised or solenoid valves are the most common trigger
• An arrestor fitted near the valve absorbs the pressure spike
• Loose pipe clips can amplify the bang by letting pipework physically jolt
• Persistent hammer can loosen joints and shorten valve life over time

What is actually going on with water hammer in pipework

In a heating system it is most often triggered by a motorised zone valve or a washing machine solenoid snapping shut quickly, sending a pressure spike back through shared pipework. Unlike expansion ticking, which happens gradually as pipes warm, water hammer is a single sharp bang timed exactly to a valve closing. A water hammer arrestor, essentially a small air cushion fitted near the offending valve, absorbs the shock before it reaches the rest of the pipework.

Where we deal with this

• Burrington (BS40) · 10 mi
• Long Ashton (BS41) · 12 mi
• Southwick (BA14) · 10 mi
• Rowde (SN10) · 14 mi
• Odd Down (BA2) · 8 mi

Questions we get asked

Is water hammer just annoying or actually harmful?

Beyond the noise, repeated pressure spikes can gradually loosen pipe joints and stress valve components over time, so it is worth addressing.

Will a plumber be able to fix it without major pipework changes?

Usually yes — fitting an arrestor near the source valve resolves most cases without needing to alter the wider pipe run.