Why do my pipes bang when I turn off a tap?
A loud thud or bang in the walls when a tap is turned off, the washing machine finishes filling or the toilet stops refilling is called water hammer. Water moving through the pipes stops suddenly, and the shock wave rattles the pipes. It's more than annoying: over time it loosens pipe clips, strains joints and shortens the life of taps, valves and appliances. The good news is it can usually be fixed.
What causes it
High water pressure
The higher the pressure, the harder the water hits when it stops. High mains pressure is the most common cause in this area. See pressure limiting valves.
Quick-closing valves
Washing machines, dishwashers, quarter-turn taps and some toilet valves shut off instantly, which creates the shock.
Loose pipes
Pipes that aren't clipped firmly move and knock against the frame or floor when the water stops.
Worn tap parts
A worn washer or jumper valve can chatter and bang when a tap is turned on or off.
How it's fixed
- Test the pressure: if it's over 500 kPa, a pressure limiting valve is often the main fix, and it protects everything else in the house too.
- Water hammer arrestors: small devices fitted near the washing machine or other quick-closing valves to absorb the shock.
- Re-clip pipes: securing loose pipes where we can reach them stops the knocking.
- Repair taps and valves: new washers, jumpers or cartridges where a worn part is the cause.
We find the cause first, then give you options and a fixed price before any work starts.
In southern Eastern Suburbs homes
Mains pressure is high in many parts of Matraville, Botany, Pagewood and Eastgardens, and older homes with timber floors often have pipes that have worked loose over the years. Put the two together and water hammer is common. Our water pressure guide explains more.
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- Local to Matraville and the southern Eastern Suburbs
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Common questions
What is water hammer?
A bang or thud in the pipes when water flowing through them stops suddenly, such as when a tap or appliance valve closes quickly.
Is water hammer dangerous?
Not immediately, but the repeated shocks strain joints and fittings and can lead to leaks over time.
Why do my pipes bang when the washing machine fills?
The machine's valves shut off very quickly. A water hammer arrestor on the washing machine taps, and lower water pressure, usually fix it.
Can high water pressure cause banging pipes?
Yes. It's the most common cause. A pressure test shows whether a pressure limiting valve is needed.
Why do my pipes whistle when the water is on?
Whistling is usually water forced through a narrow spot at high pressure, such as a partly closed or worn valve, a worn tap washer or a pressure limiting valve. Testing the pressure and checking valves usually finds it.
Related help: pressure limiting valves, water pressure guide, taps and toilets and flexi hoses. Local pages: Matraville, Botany, Pagewood and Eastgardens.