What Causes Rattling Pipes?

by Michael Franco
illustration of rattling pipes in a basement

Your home’s plumbing system can feel like a bit of a mystery, with its largely hidden pipes and all that behind-the-scenes action. But the mysterious can quickly turn unsettling if your pipes begin rattling or making a banging noise.

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It’s true that rattling pipes can be rather unnerving, but the good news is that rattling doesn’t usually indicate a major problem. And in some instances, you may even be able to troubleshoot these loud pipes yourself. Read on to learn what causes rattling water pipes so that you can get that coveted quiet back in no time.

Why Are My Pipes Rattling, Banging or Knocking?

The first thing to identify with noisy pipes is when the sound is occurring. Does this noise start shortly after turning off a faucet? If your pipes make a rattling, banging or knocking noise after shutting a faucet off, the most likely culprit is a phenomenon called water hammer.

Wait ... What Is a Water Hammer?

When a water faucet is suddenly turned off, the flow of water running through the pipe hits the valve blocking it from continuing down the pipe. This water is moving quickly and with quite a bit of pressure, and when it slams against the valve and surrounding pipe, a rattling or crashing can result — especially if the pipe shakes and hits other pipes or even walls.

Not all homes deal with water hammer issues. New homes built after the 1990s usually come with built-in water hammer arrestors that are meant to prevent water hammer. However, the plumbing systems installed in homes built between the 1970s and 1990s weren’t typically equipped with anything to alleviate water hammer. But the good news here is that water hammer arrestors can be added to existing plumbing to help stop pipes from rattling. Houses built before the 1970s often have air chambers built into their plumbing systems to combat water hammer, but these often fill with water over time and eventually stop working effectively. Luckily, these systems can also benefit from the addition of an arrestor.

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Other Reasons for Rattling

If your plumbing has air chambers that are still functioning, or if you already have water hammer arrestors, there may be another issue at play that’s causing your pipes to make noise.

Loose Pipes

If the rattling is not limited to occurring after turning off a faucet abruptly, it could be that the straps connecting your plumbing pipes to the wall studs are loose, which can cause pipe vibration and a sound of knocking pipes. If loose pipes are your issue, you may need to tighten their straps. In some instances, you may just be able to surround loose pipes behind a wall with extra padding to help stop the banging noise.

High Water Pressure

It could also be that your water pressure is too high. If your water pressure is too high for your home’s capacity, it can cause the pipes to vibrate. This can sound like a humming noise, most noticeably when the water is still running. Try adjusting the water pressure in your home and see if the sound disappears at a lower pressure point.

Loose Fittings

Knocking pipes could also be caused by loose fittings. Pipework may eventually loosen with time and age, or it could be that the fittings weren’t installed securely to begin with. In either case, the fix here is a simple one, as you’ll just have to tighten or refit the offending pipework. Pipe repair tape can also sometimes be used here to help secure loose fittings and alleviate the banging or knocking sound.

Sediment Buildup

If the noises seem to be happening randomly, even when there’s no water running, it could be that you have a buildup of sediment at the bottom of your water heater. Steam bubbles from that sediment can reverberate, causing a banging noise. If you think sediment is to blame for your noise issue, you’ll need to call in a plumber to inspect the situation, or you could try draining your water heater yourself.

How Do I Stop My Pipes From Rattling?

Once you’ve determined the reason your pipes are making noise, you can either get to work on fixing it yourself or give a plumber a call. Plumbing repairs are rarely inexpensive, but as far as plumbing issues go, rattling pipes are typically some of the easier issues to solve.

If the noisy pipes are due to a water hammer issue, you can add arrestors to your pipes to fix the problem. If the knocking noise stems from another issue — like loose pipes or fittings, sediment buildup or high water pressure — you can use the notes above to determine whether you should call in a plumber.

Regardless of why your pipes are noisy, with a little work, you can hopefully banish that knocking noise from your pipes forever. Now, if only you could get those door-to-door salesmen to stop their knocking.

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