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“Water Hammer”: The Weird Knocking Sound from Your Pipes


We would wager that 90% of the time someone believes their house is haunted because of strange noises coming from the walls, the problem is actually with the plumbing. Old or faulty plumbing can sometimes make weird or startling sounds. The most common of these noises is known as water hammer, a fearsome sounding name but appropriate because it sounds like a hammer striking against the pipe metal.

What is it, and should you be concerned about it?

Water hammer and shockwaves

The simple explanation for water hammer is that it’s the result of a shockwave created when water stops abruptly in the pipes. If you remember high school science, you’ll know that the energy of a wave will continue forward if halted as another form of energy, and in this case, it’s a pressure shockwave that creates a sharp clang sound.

Why is water suddenly stopping in the pipes? This always happens when you turn off a faucet or if an appliance stops the water flow into it. And if you’re now thinking, “Why don’t I hear this noise all the time?”, that’s where we get into why water hammer is warning of a problem.

What water hammer may be telling you

Because causing water to stop creates a shockwave, plumbing is designed to create a cushion for the wave. The plumbing in your house is built with air chambers that create a barrier for the shockwave whenever a tap shuts off. That’s why you don’t hear a clang each time you shut off the bathroom sink when you’re brushing your teeth. If you do hear water hammer, it probably means the air chambers in the plumbing have become water-logged.

Another possibility is a solenoid valve shutting too fast, which triggers the shockwave. Water hammer can also be a sign that the water pressure in the plumbing is too high: water hammer is more common in high-pressure water systems, which your house is not supposed to be!

You do not want to allow water hammer to continue, even if you think you can tolerate the noise. The vibrations moving through the pipes are damaging. They will start to cause pipes to shake loose, and the force of the impact can also damage appliances. If high water pressure is the source, that’s also something you want to correct because of the damage it can create throughout the plumbing. 

What can be done about water hammer

Thankfully, with the assistance of a professional plumber with all the know-how about plumbing in Hudson, OH, you can have water hammer corrected. When our plumbers come to your home, they’ll examine the pipes to find the source of the noise.

If it’s high water pressure, they can put a device called a water pressure arrestor onto the water main that will lower the pressure to a normal level (below 80 psi). They can add water chambers to pipes that don’t have air cushions, which involves putting on a vertical section of pipe to relieve pressure. They can fix solenoids. For extremely old pipes, they’ll probably recommend some level of repiping. You can trust our team to find the best solution for your home.

Crown Group Ohio—Your comfort experts since 1963. Call us for plumbing service in Stark and Summit counties.

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