If you've ever heard a loud bang or shudder when a tap closes or a washing machine valve shuts off, you've experienced water hammer. It's more than just an annoying noise — over time, the pressure shockwaves can loosen pipe fittings, damage valves, and eventually cause leaks. Here's what causes it and how it's fixed.
What is water hammer?
Water hammer is a pressure surge that occurs when flowing water is suddenly stopped — for example, when a tap is closed quickly or a solenoid valve in a washing machine or dishwasher snaps shut. The moving water's momentum has to go somewhere, and the resulting pressure wave travels back through the pipe as a shockwave, producing the characteristic bang.
What does water hammer sound like?
Water hammer is typically a sharp, single bang or a series of rapid bangs when a valve closes. It's distinct from the continuous humming or vibrating you might hear from pipes that aren't properly secured. If you hear a bang specifically when a tap or appliance shuts off, that's water hammer.
What causes water hammer?
- Fast-closing valves — washing machines and dishwashers have solenoid valves that snap shut instantly, producing the sharpest water hammer.
- High water pressure — the higher the pressure, the more energy the water carries and the louder the hammer. Homes with high mains pressure are more prone to it.
- Lack of air chambers or arrestors — older homes may have air chambers (vertical pipes that act as shock absorbers) that have filled with water over time, losing their cushioning effect.
- Loose pipes — pipes that aren't properly secured amplify the noise as they move with the pressure wave.
Can water hammer damage plumbing?
Yes. Over time, repeated pressure shockwaves can loosen pipe joints and fittings, damage valves and washing machine hoses, and eventually cause leaks. It's not an immediate emergency, but it shouldn't be ignored — the damage is cumulative.
How is water hammer fixed?
Install water hammer arrestors
A water hammer arrestor is a device containing a sealed air chamber or piston that absorbs the pressure surge. It's installed near the source of the hammer (often at the washing machine or dishwasher connection). This is the most effective fix for hammer caused by fast-closing appliance valves.
Drain and recharge air chambers
If your home has older air chambers that have filled with water, draining the entire system and refilling it can restore the air cushion. Turn off the main water supply, open all taps to drain the system, then turn the water back on. This is a simple fix but may not be permanent, as the chambers can refill over time.
Reduce water pressure
If your mains pressure is high, installing or adjusting a pressure-limiting valve reduces the energy in the system and can significantly reduce water hammer. A plumber can test your pressure and advise whether this is appropriate.
Secure loose pipes
Pipes that aren't properly secured amplify the noise. Securing loose pipes with appropriate clips reduces the movement and the noise, though it won't eliminate the underlying pressure surge.
When to call a plumber
If recharging the air chambers doesn't solve the problem, or if the hammer is loud and frequent, a plumber can diagnose the cause, test your water pressure, and install arrestors or a pressure-limiting valve. Because water hammer can damage fittings over time, it's worth fixing rather than ignoring. Contact our Gold Coast team to arrange a diagnosis.
Frequently Asked Questions
Need a Gold Coast Plumber?
If you're dealing with a plumbing problem and need professional help, our local team is ready to assist.
