Water Hammer: What It Is, Why It Happens, and How to Stop It for Good

Heard loud banging noises coming from your pipes? That’s likely water hammer—a surprisingly common issue in plumbing systems that sounds worse than it looks… until it starts damaging your pipes.

This guide will break down exactly what water hammer is, how to identify it, what causes it, and most importantly—how to stop water hammer and prevent it from coming back.

Let’s dive in.

What Is Water Hammer?

Water hammer is the term used when you hear that sudden, loud “bang” or knocking noise in your plumbing system. It’s not just annoying—it’s a shockwave of pressure caused by the sudden stoppage or redirection of water flow.

Here’s what happens in plain terms:

1. Water is rushing through your pipes.
2. A valve suddenly closes—bam.
3. The water has nowhere to go, so it slams against the shut valve or pipe wall.
4. That shock creates a pressure wave—often called the hammer effect—that echoes through the pipes.

Over time, these shockwaves can do real damage to your plumbing.

What Triggers Water Hammer?

It usually kicks in when valves close too fast, but there are several contributing factors. Let’s break them down.

Fast-Closing Valves

Appliances like washing machines and dishwashers shut off water flow quickly. That rapid closure can trigger a sudden pressure surge, a classic cause of water hammer.

High Water Pressure

Too much water pressure makes everything worse. It amplifies the force of the shock when water stops suddenly, making the banging sound louder and the risk of pipe damage higher.

Loose Pipes

When pipes aren’t properly fastened, they can vibrate or bang against nearby surfaces. This movement worsens the sound and increases the chance of long-term damage.

Faulty or Waterlogged Air Chambers

Some plumbing systems have vertical air chambers that help absorb shock. But if they fill with water over time, they lose their cushioning effect.

Pump Failure or Valve Wear

If a pump suddenly shuts off or a valve becomes worn, the system might not handle pressure changes well—again leading to the hammer effect.

How to Know It’s Water Hammer

Wondering if those loud bangs are really water hammer?

Here are common signs:

• Banging or knocking noises when turning off water
• Pipes visibly shaking behind walls
• Occasional echoes or vibrations after the noise
• Only happens with certain appliances or faucets

If your pipes sound like someone’s hitting them with a wrench every time you shut off the tap, you’re probably dealing with it.

How to Fix Water Hammer (Step-by-Step)

If water hammer is keeping you up at night or threatening your plumbing, here’s how you can fix it. The good news? Many solutions are DIY-friendly.

Step 1: Check Your Water Pressure

• Use a pressure gauge to test the water pressure.
• Ideal range is between 40–60 psi.
• If it’s higher, adjust the pressure-reducing valve—usually located near where your main water line enters the home.
• Turning it counterclockwise will lower the pressure.

Why it helps: Lower pressure reduces the force of the water, which softens or eliminates the hammer effect.

Step 2: Drain the Air Chambers

If your home has built-in air chambers (small vertical pipes near shutoff valves), they might be waterlogged.

Here’s how to drain them:

1. Turn off the main water supply.
2. Open the highest faucet in the home (like an upstairs sink).
3. Open the lowest faucet (like a basement or outdoor spigot) to drain the system.
4. Once water is drained, close the faucets and turn the water back on.

Why it helps: Air refills the chambers, restoring their shock-absorbing power.

Step 3: Install Water Hammer Arrestors

If you don’t have air chambers—or if they’re not enough—water hammer arrestors are your next best bet.

These devices have air-filled chambers or springs that absorb the force from pressure waves.

• Choose between in-line, screw-in, or capped vertical arrestors.
• Install them near appliances like dishwashers or washing machines.
• Use plumber’s tape and tools like a wrench or soldering torch as needed.

Why it helps: Arrestors offer long-term protection without regular maintenance.

Step 4: Tighten and Secure Loose Pipes

Grab a flashlight and check behind walls or under floors where you can access piping. Look for:

• Pipes that wiggle or move when touched
• Missing or loose straps

Use U-shaped pipe straps or padded hangers to secure them tightly to studs or joists.

Additional tip: Use foam pipe insulation to cushion the pipes and reduce vibration.

How to Prevent Water Hammer From Happening Again

Once you’ve fixed the issue, prevention is key. Here’s how to keep your pipes quiet and healthy for the long haul.

Regular Maintenance Tips

• Keep water pressure below 50 psi if possible.
• Check and drain air chambers every few months.
• Secure any new piping immediately during renovations.
• Replace worn valves or gaskets as needed.

Proactive Installations

• Use air chambers or arrestors when installing new appliances.
• Install air-relief valves at high points in your system to release trapped air.
• Choose valves that close more slowly if available.

Consider Upgrades

• If replacing your entire plumbing system is on the table, choose pipes with built-in chambers or cushion features.
• Replace pressure regulators every few years or as they wear down.

The Hidden Dangers of Ignoring Water Hammer

You might think, “It’s just a noise—can’t be that serious.” But over time, water hammer can cause:

• Burst pipes
• Leaky joints and fittings
• Broken valves or gaskets
• Structural damage behind walls or under floors
• Electrical hazards from hidden leaks

Fixing a small water hammer issue today could save you thousands in plumbing repairs tomorrow.

Final Thoughts

Water hammer might seem like just a minor nuisance, but it’s a plumbing issue that shouldn’t be ignored. The loud banging is more than a sound—it’s a warning sign. By understanding what causes water hammer and how to fix it, you can protect your home, extend the life of your plumbing, and enjoy a little peace and quiet too.

Simple steps like lowering water pressure, draining air chambers, or installing a water hammer arrestor can make all the difference. Start with a pressure check. Then follow the steps above to get your pipes running smooth and silent again.

Call 1-Tom-Plumber 

Don’t hesitate to contact us here or call us at 1-Tom-Plumber (1-866-758-6237) if you need any plumbing, drain cleaning, water damage, or excavation service. 1-Tom-Plumber’s certified team of plumbers and drain technicians respond immediately to any emergency plumbing, drain cleaning, or water damage problem. We also handle the excavation of underground water lines and sewer main lines. Our immediate-response team is available every day and night of the year, even on holidays.