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That Strange Sound From the Pipes? It’s Called Water Hammer


It’s a quiet day in your home, and you’re washing your hands at the kitchen sink. You turn off the tap, and suddenly a loud and surprising bang! sound leaps out from the walls. A sound like a hammer striking against metal. 

What was that?

It’s a plumbing phenomenon called water hammer—for reasons you can probably already figure out. This is a common problem in residential plumbing and one that will often take a Burlington, VT plumber to fix. First, let’s take a look at what water hammer is, why it’s a problem, and why it might occur in your plumbing. Once you have that information, we can tell you how we can help resolve the problem.

Water Hammer Comes From a Shockwave

Whenever you turn on a tap in your house or a water-using appliance starts working, water flows from the pipes toward it. This water has momentum and when the tap shuts or the appliance cuts off the demand for water, the water stops abruptly. This creates a shockwave. However, air cushions inside the plumbing absorb the shockwave. If those air cushions are not present, the shockwave creates the sound of water hammer. Worse, the shockwave causes the pipe to vibrate and move around.

The Problem With Water Hammer

Aside from creating an annoying and startling noise, the reason you don’t want water hammer happening in your plumbing system is because it can damage pipes and appliances. The sudden impact of the shockwave can cause pipes to abrade against surfaces or even break loose. (This will, by the way, increase the sound of water hammer.) It can create leakage at joints in the pipes or even cause pipes to burst. 

The Causes of Water Hammer

There are several reasons that pipes can lose the cushion that absorbs the shockwave that creates water hammer. It can be worn stop valves, water-logged air chambers, solenoid valves acting too fast to close off a pipe, or loose piping. If you live in a home built before 1970 and haven’t had extensive repiping done, it’s likely that worn stop valves are creating the problem. Water-logged air chambers are also common. 

Stopping Water Hammer

Now we come to the bottom line: How do you stop water hammer? 

The best way is to call our professional plumbers. There are several solutions to the problem depending on what’s causing it. If your plumbing is mostly up-to-date with modern materials, our plumbers will restore air chambers or add them. Adding air chambers requires we put in a length of vertical pipe right behind the valve where the water hammer is occurring. This creates an air chamber to absorb the shockwave. If your plumbing already has air chambers, we’ll drain them of water so they work again.

For older homes, we’ll recommend new piping and stop valves be put in, and we’ll include air chambers with them. We may offer advice about other upgrades you can make to the plumbing: the occurrence of water hammer is often a warning of other issues with aging pipes in the house.

Schedule plumbing services with our team today. Red Rock Mechanical, LLC serves Northwest Vermont and Northeast New York.

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