How to Stop Your Knocking, Banging Pipes

If your home’s pipes are making knocking and banging noises, you likely have one of the following problems:

  • Water hammering
  • Expanding/contracting hot water pipes
  • Loose pipes vibrating when water is running

So how do you know which problem you have and how to fix it? Well, you can pinpoint your particular problem by first determining when you hear the noises. We’ll explain more below.

Does your home have old pipes?

It may be time to consider repiping.

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If your pipes make noises right after a water appliance is turned off…

…you most likely have an older home with water hammering problems.

You see, older homes in the Fort Myers area were built with ineffective “air chambers” that are supposed to prevent water hammering problems. But because air chambers are prone to failure over time, these older homes will often experience banging pipes due to water hammering.

So what exactly is “water hammer”?

Water hammer happens when a valve suddenly closes, forcing all the water flowing through the pipes to collide into the closed valve. That sudden, violent collision creates shockwaves that shake your pipes (creating the annoying banging noises you hear).

And beyond causing some scary noises, the forceful vibrations of water hammer can actually destroy your pipes over time.

Why “air chambers” in older homes are ineffective:

Air chambers are basically T-sections of pipe that stick out perpendicularly from a plumbing line. They provide an alternate route for rushing water when a valve suddenly closes in the plumbing line. At the tip of the pipe is a pocket of air that “cushions” the water hammer.

But air chambers are highly inefficient because rushing water can easily absorb that pocket of air over time (see picture below). And once the air pocket is completely gone, there’s nothing left to cushion shock waves in the water.

Check out this video for an explanation of how air chambers get displaced with water.So how do you fix water hammer?

Well, first off, newer homes built today are required by code to have a much more effective water hammer prevention device called “water hammer arrestors”. So, if you have an older home, we highly suggest replacing those air chambers and upgrading to water hammer arrestors.

Water hammer arrestors work the same way as air chambers but are mechanically operated, meaning rushing water is absorbed by a sliding piston that protects the air cushion. Water hammer arrestors very rarely go bad.

If your pipes are knocking when hot water is turned on…

…you likely have pipes that are expanding and grinding against walls or joists.

All kinds of pipe material expands in hot temperatures. So, if you hear the banging/knocking noises only when you run hot water, it may be piping that’s expanding and contracting as hot water runs through it. And as those pipes swell, they can rub and bump against surrounding metal, causing the banging/knocking noises you hear.

So how do you prevent pipes from expanding?

Well, unfortunately you don’t. Residential piping will always expand slightly in hot temperatures; there’s no getting around that.

However, you can pinpoint the faulty pipe and wrap foam insulation around the rubbing area to prevent it from bumping against nearby metal parts. A professional plumber can quickly pinpoint trouble pipes and make the most effective adjustments that will prevent banging pipes.

If your pipes make noises every time water is turned on…

…your home’s water pressure is probably causing loose pipes to vibrate against their surroundings.

Now, it’s important to note that in the Fort Myers area, we receive water from our municipal water supplier at a safe pressure—anywhere from 55 to 65 psi (pounds per square inch).

So, while it’s unlikely that your home is dealing with extremely high water pressure (anything over 80 psi), it’s still possible that loose pipes are knocking against their surroundings as water rushes through them.

If your pipes vibrate when hot water is turned on…

We suggest you have a professional come examine your home’s plumbing for loose piping.

They’ll be able to determine which pipes are vibrating and knocking. From there, they can use foam insulation or tighten/add mounting straps to the trouble pipes and prevent any annoying noises in the future.

Still not sure why your pipes are making noise> If you need a professional to diagnose your banging pipe problems, we can help. Just contact us and we’ll send an experienced plumber to investigate!

Further Reading:

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