Banging or hammering when taps are used
Water hammer is one of those plumbing issues that sounds far worse than it actually is — that startling bang or clunk when you turn a tap off is enough to make anyone worry they've got a serious problem on their hands. The good news is that it's a common occurrence in many UK homes, particularly in older properties or those with high mains water pressure, and it's almost always fixable without calling in a professional. What's happening is that the water flowing through your pipes is being suddenly stopped, creating a pressure shockwave that reverberates through the pipework and causes it to vibrate against walls, joists, or whatever else it's near. This guide walks you through the practical steps to diagnose and cure water hammer yourself, from simple tightening of pipe clips right through to fitting an arrestor if needed. If you've tried these steps and the banging persists, or if you're uncertain about any aspect of your plumbing system, it's worth getting a qualified plumber to have a look.
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Most likely cause & what to check
This is almost always "water hammer" — a pressure shockwave caused when water flow is suddenly stopped.
Check all visible pipe clips — loose pipes bang against joists or walls. Secure with new clips.
Wrap foam pipe lagging around pipes where they pass near timber.
Slightly reduce mains water pressure by turning the stop tap a quarter-turn clockwise.
If severe, fit a water hammer arrestor (£15–£30) on the rising main near the stop tap.
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Frequently asked questions
Is water hammer dangerous to my plumbing system?
Water hammer itself won't cause immediate damage, but repeated shock waves can gradually weaken joints and fittings over time. That's why it's best to sort it sooner rather than later — it's not urgent, but it does need addressing to protect your pipework long-term.
Why does water hammer happen more in some homes than others?
Homes with higher mains water pressure are more prone to it, as are properties with older, less secure pipework or loose clips. Modern homes with properly fitted and secured pipes tend to experience it less frequently, though it can happen anywhere.
Can I reduce water pressure myself, or do I need a plumber?
You can safely reduce it yourself by turning your stop tap (usually under the kitchen sink or outside) a quarter-turn clockwise — it's a simple five-second job that many homeowners do without assistance. If you're not confident locating your stop tap, a plumber can show you where it is on your first visit.
How much does a water hammer arrestor cost to fit?
The arrestor itself costs between £15 and £30 from any plumber's merchant, and fitting is straightforward if you're comfortable with basic plumbing, or a plumber can install one for a modest call-out fee. It's a cost-effective solution that often solves the problem permanently.
Will wrapping pipes in lagging really stop the banging?
Lagging dampens vibration and can reduce the noise noticeably, especially where pipes pass close to timber joists or walls. It won't eliminate water hammer entirely, but it's a useful part of the solution when combined with securing loose clips and adjusting pressure.
How do I know if it's water hammer or a different plumbing problem?
Water hammer produces a distinctive loud thud or bang when you turn a tap on or off — it's sudden and loud. If the noise is more of a continuous rattle, hissing, or grinding sound, it may be a different issue worth investigating further.