If you’ve ever heard a loud bang or thud coming from your pipes after turning off a tap or appliance, there’s a good chance you’re dealing with water hammer. While the noise itself can be alarming, it’s a well-known and fixable plumbing issue.
In most cases, the cause can be identified and resolved before it leads to serious damage. Whether the problem is high water pressure, loose pipes, or faulty valves, understanding what’s happening inside your plumbing system is the first step toward a solution.
Below, we’ll explain what causes this issue, how to stop water hammer yourself, and when it’s time to call a licensed plumber.
You may also notice water hammer alongside other plumbing issues, such as noisy or leaking toilets. If that’s the case, professional toilet repairs may help address the underlying pressure or valve problems contributing to the noise.
What is water hammer and what does it sound like?
Water hammer, also known as hydraulic shock, happens when flowing water is forced to stop suddenly inside your pipes. This creates a pressure wave that travels through the plumbing system, causing pipes to shake or bang.
It can sound different depending on the cause, which is why it’s important to distinguish true water hammer from other plumbing noises.
Sound description | Likely cause | Water hammer or not? |
Loud bang when a tap or appliance shuts off | Sudden valve closure creates a hydraulic shock | Yes |
Rattling during water flow | Loose pipe brackets or unsecured pipework | No |
Tapping or ticking when pipes heat up | Thermal expansion of hot water pipes | No |
Constant hissing sound | Pressure issue, leaking valve, or faulty fixture | No |
In modern Australian homes, water hammer is especially common with washing machines, dishwashers, and mixer taps that use fast-closing valves.
What causes water hammer in Australian homes?
Wondering what causes water hammer? Most of the time, it comes down to four main causes: sudden valve closure, high water pressure, waterlogged air chambers, and loose pipes.
Sudden valve closure
This is the most common cause of water hammer. When water flow stops abruptly, the momentum creates a shockwave through the pipes.
Quarter-turn mixer taps and solenoid valves in washing machines and dishwashers are major culprits in newer Australian homes because they shut off water almost instantly.
High water pressure
High water pressure makes water hammer worse because the shockwave has greater force behind it. Sydney Water generally recommends residential water pressure between 350 and 500 kPa. Anything above this can increase stress on pipes, fittings, and appliances.
Waterlogged air chambers
Some plumbing systems contain air chambers designed to cushion pressure changes. Over time, these chambers can fill with water and stop working properly, allowing pressure shock to travel through the system.
Loose or unsecured pipes
Loose pipes amplify the sound of water hammer. Even minor pressure surges can create loud banging if pipes aren’t properly secured.
Is water hammer actually damaging your pipes?
Water hammer noise is not usually an immediate emergency, but repeated pressure surges can cause cumulative damage over time.
The constant shock can loosen pipe joints, wear out valve seats, strain appliance connections, and in severe cases, contribute to burst pipes. Washing machine and dishwasher hoses are especially vulnerable because they experience repeated pressure changes during normal use.
Sustained high pressure may also affect appliance warranties, including those for hot water systems, dishwashers, and washing machines.
While water hammer might seem like a minor annoyance at first, leaving it unresolved can eventually lead to more expensive plumbing repairs.
Step-by-step instructions on how to fix water hammer yourself
Before you begin, make sure you have:
- A water pressure gauge
- Access to the main water supply valve
- Access to the affected pipes or appliances
Keep in mind that any work involving mains pressure pipework or plumbing alterations must be carried out by a licensed plumber under NSW regulations.
Step 1: Flush the air from your pipes
Turn off the main water supply, then open the highest and lowest taps in the house to drain the system. Once the water stops flowing, turn the supply back on slowly. This can help restore air pockets inside air chambers and reduce pressure shock.
Step 2: Check and reduce water pressure
Use a pressure gauge on an outdoor tap to check your household pressure. If it’s consistently above 500 kPa, high pressure may be contributing to the problem.
A faulty pressure limiting valve (PLV) may need adjustment or replacement by a licensed plumber.
Step 3: Secure loose pipes
Inspect any exposed pipes under sinks, in cupboards, or under the house. If pipes move or rattle when water flows, they may need additional brackets or cushioning clips. Securing the pipes will help reduce movement and noise.
Step 4: Install a water hammer arrestor
A water hammer arrestor is designed to absorb pressure shock before it travels through the plumbing system. These are commonly installed near washing machines, dishwashers, or fast-closing taps and are often the best long-term solution.
How to prevent water hammer from coming back
Preventing water hammer usually comes down to reducing sudden pressure changes and keeping your plumbing system properly maintained.
Helpful prevention measures include:
- Installing slow-close taps and valves
- Scheduling periodic plumbing pressure checks
- Fitting water hammer arrestors during renovations or appliance replacements
- Monitoring changes in water pressure or noise intensity over time
A simple annual plumbing checklist can also help catch issues early:
- Test the household water pressure
- Inspect visible pipe brackets
- Check appliance hoses for wear
- Listen for new banging or rattling noises
When should you call a licensed plumber for water hammer?
You should contact a licensed plumber if:
- DIY fixes have not stopped the noise
- The banging is coming from inside the walls or under the floors
- Water pressure reduction is needed at the mains
- Pipe joints or fittings are leaking
- The issue affects a hot water system or a gas-connected appliance
Under the Plumbing and Drainage Act 2011 (NSW), licensed plumber sign-off is needed for work involving mains pressure systems or plumbing alterations.
Good Hands Plumbing has years of experience with water hammer repairs across Sydney homes. Our team can identify the cause of your problem and recommend the best long-term fix.
To arrange an inspection or speak with an experienced plumber, contact us today.
Frequently Asked Questions
How much does water hammer repair cost in Sydney?
The cost will depend on the cause. Minor fixes, such as securing pipes or installing a water hammer arrestor, are generally affordable, while pressure valve replacements or concealed pipe repairs may cost more.
Is water hammer dangerous?
Not usually in the short term, but repeated pressure surges can damage plumbing systems over time and increase the risk of leaks or pipe failures.
Will water hammer go away on its own?
Usually not. The underlying issue will remain until properly addressed.
Can water hammer affect my hot water system or appliances?
Yes. Water hammer can place stress on hot water systems, dishwashers, washing machines, and connected pipework, which can shorten appliance lifespan.
