Noisy Pipes and Water Hammer: What Causes It and How to Fix It

What is water hammer?

Water hammer is a loud banging or knocking sound in the pipes, usually when a tap or valve shuts off suddenly. When fast-flowing water is stopped abruptly, the momentum creates a pressure wave that slams through the pipes. It sounds alarming and, over time, can damage joints and fittings.

Common causes

• Quick-closing valves - washing machines, dishwashers, and modern lever taps shut off very quickly, which can trigger water hammer
• High mains pressure - if the incoming water pressure is above 4 bar, the force behind the water makes hammer more likely
• Loose pipework - pipes that are not properly clipped to walls or joists will rattle and bang as water flows through them
• Air in the heating system - air pockets cause gurgling and trickling noises in radiators and pipes
• Thermal expansion - hot water pipes expand and contract as they heat up and cool down, causing ticking or creaking sounds

DIY fixes

• Bleed your radiators - if the noise is gurgling or trickling from the heating system, bleeding the radiators releases trapped air
• Check pipe clips - tighten any loose clips where pipes pass through walls, floors, or joists
• Turn down the stopcock slightly - reducing the flow rate can reduce water hammer, though this is a workaround not a fix

Professional fixes

• Mini expansion vessels (water hammer arrestors) - fitted near the appliance causing the problem, these absorb the pressure wave. They cost around £30-£60 fitted
• Pressure reducing valve - if your mains pressure is too high, we can fit a PRV to bring it down to a safe level (around £150-£200 fitted)
• Pipe re-clipping - securing loose pipes properly eliminates rattling and banging
• System flush - if debris is causing blockages that restrict flow and create noise, a power flush can resolve it

When to call us

Occasional creaking from hot pipes is normal. Persistent banging, especially when appliances turn on or off, needs investigating. Left unchecked, water hammer can weaken pipe joints and cause leaks. Call us on 01932 943 009 and we will find the source and fix it.