What is Water Hammer and How to Fix It

Have you ever heard a loud banging sound after turning off your tap or flushing the toilet? That’s called water hammer. It’s a common plumbing issue that happens when water flow stops suddenly and sends shockwaves through your pipes.

What is water hammer?

Water hammer is also known as hydraulic shock. It happens when fast-moving water is forced to stop or change direction suddenly. The result is a water hammer noise - a loud bang, thud, or knocking sound coming from your pipes.

This sound isn’t just annoying. Over time, it can damage pipes, loosen joints, and cause leaks. Knowing how to fix water hammer early can help prevent expensive repairs later.

What causes water hammer?

There are a few main causes of water hammer:

• High water pressure: When pressure is too high, water stops suddenly with more force.
• Quick-closing valves: Appliances like washing machines or dishwashers shut off water instantly, creating a shockwave.
• Loose pipes: Unsecured pipes can move and bang against walls when the water flow changes.
• Worn air chambers or arrestors: These parts absorb pressure surges, but over time they can fill with water or fail.

Understanding these causes is the first step in learning how to stop water hammer effectively.

How to fix water hammer

There are a few practical steps to quieten your pipes and protect your plumbing.

1. Check and reduce water pressure

Use a pressure gauge to test your water pressure. It should be between 40 and 60 psi.
If it’s too high, install a pressure-reducing valve. Lowering the pressure can often stop water hammer noise instantly.

2. Secure any loose pipes

Loose pipes vibrate and knock against walls. Use pipe clips, brackets, or foam insulation to hold them in place and reduce movement.

3. Drain and refill your plumbing system

Older homes may have air chambers that get waterlogged. Turn off the water supply and drain your pipes completely. When you turn the water back on, the chambers refill with air and absorb pressure again.

4. Install water hammer arrestors

If the problem keeps coming back, install water hammer arrestors near noisy appliances. These small devices use air cushions to absorb shockwaves. They’re one of the most reliable water hammer fixes for modern homes.

5. Replace worn valves or washers

Old or faulty valves can close too quickly. Replacing them with slow-closing options can help stop the sudden pressure change that causes water hammer.

How do you stop water hammer for good?

If you’ve tried these steps and the noise continues, call a professional plumber. Persistent water hammer noise could mean a deeper issue like incorrect pipe sizing or missing arrestors. A professional can find and fix the root cause safely.

Now you know what water hammer is and how to fix it. It’s a common but preventable problem. By lowering your water pressure, securing pipes, or installing arrestors, you can protect your plumbing and enjoy a quieter home.

Understanding how to stop water hammer not only prevents damage but also keeps your water system running smoothly for years to come!

If you have any more questions concerning water hammer and how to fix it, or you require any additional information about the plumbing products we sell at Howarth, please visit your local Howarth branch, or contact our customer services on 01472 907051.

You can also explore our range of plumbing products here, and you can even visit us in branch for more information.