What Causes Banging Pipes When Water Is Not Running?

From cooking, taking a bath, or doing laundry, chances are you’re using your plumbing system every single day. However, sometimes, your pipes can start making noise. What causes banging pipes when water is not running and is this a dangerous issue?

No one wants plumbing issues, especially at the time you’re not expecting them. Still, even your pipes have a lifespan, and they are not eternal. Sooner or later, they might go awry. When this happens, you might hear strange voices coming from them.

When you hear banging pipes when water is not running, this means something is wrong with your pipes. It’s almost as if they’re communicating with you, trying to let you know that they’re not okay.

If you’re faced with this issue, here’s what you should do!

Why You Have Banging Pipes When Water Is Not Running?

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Pipes can make all sorts of noises. This includes, but it’s not limited to:

  • Banging
  • Humming
  • Gurgling
  • Whining
  • Squealing
  • Rattling

If you have banging pipes when water is not running, you should consider yourself lucky. Noise coming from the pipes is a sign of some underlying issue that might have otherwise gone unnoticed until you have a severe leak or even a burst pipe!

This type of noise can even be called water hammers. Water hammers, while being one of the most common sounds your pipes make, are some of the weirdest ones, as well. They usually happen when the water is suddenly shut off while the water pressure is high. The water has nowhere to run to, so pipes are forced to make a loud banging noise.

To explain this further, imagine this: A water that runs from your pipes through your faucet is pushed at high pressure, or rather at a high force level and high speed. Once something shuts off the water, retraction happens, releasing a lot of energy. This energy cannot just disappear – it needs to go somewhere.

Here are some of the most common reasons behind the banging pipes when water is not running:

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1.Lack of Cushioning Force

Usually, there is an air chamber located behind the wall that holds your pipes. When the retraction occurs, the water rushes back through the vertical plumbing pipes before hitting the air chamber. The cushioning force that happens will prevent the water from banging against the walls of the pipe.

However, certain pipe damages can cause the loss of air in that vertical wall chamber. This means there will be no more air cushion that can soften the force of the running water. This will end with banging pipes when water is not running.

These damages can be caused by:

  • Faulty water flow
  • Inadequate water pressure
  • The pressure valve shuts off too quickly

2.Loose Piping

Most of the time, banging pipes when water is not running is caused by loose plumbing.

The high pressure is responsible for water reaching your faucets in mere seconds after you’ve turned it on. However, if pipes aren’t tightly fitted against the frames that should hold them in place, they will vibrate. Sometimes they’ll even bang up against these frames! This is what’s causing the hammering noise you typically hear.

These hard hits against the frame can result in pipe leaks. This can lead to not only water loss but also corrosion or green copper pipes. Over time, this can result in bursts.

3.Excessive Water Pressure

Low water pressure isn’t the only pressure-related issue that can happen with your pipes. Having excessive water pressure is also bad for the pipes.

While high pressure usually causes high noises, it can sometimes result in banging noise in pipes.

Anything above 75psi is considered too high and even dangerous as it can make the pipes vibrate and make all sorts of noises. [1]

How To Fix Water Pipes Banging?

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There are many things you can do about noisy plumbing. However, when you have determined that you truly have banging pipes when water is not running, you’re already one step closer to the solution. This type of noise doesn’t have as many possible causes as some other noises that can occur.

Here are two solutions for fixing your piping problem, depending on when you hear the noise:

1. Knocking Happens When You Shut Off the Cold or Hot Water Supply

Here are some common scenarios for banging pipes when you shut off the cold or hot water supply:

  • Pipes in the bathroom wall are banging once the toilet is flushed.
  • Banging noise occurs in the laundry room once the clothing washer is done with filling.
  • A loud banging noise happens in the water pipes once the sprinkler system shuts off.

The most likely cause behind this is a water hammer. While people use this term for a loud banging noise inside your pipes, it’s actually a name of a specific phenomenon.

A water hammer happens once a water valve is shut off without warning. The water from the pipes crashes into the valve, which will shake your pipes and create a banging noise. This can result in loose pipes and even major leaks.

To fix this problem, you need to know how old your piping is.

If your home was built before the ‘60s, your pipes probably have air chambers. This part of the pipe contains air and behaves as a shock absorber. Sometimes, though, these chambers can be filled with water, especially if the pipes haven’t been replaced for many years.

If your home has air chambers, you need to drain the water out of your plumbing before refilling it. Here’s how to do so:

  • Turn off the water at the main valve.
  • Open the highest faucet inside your home.
  • Open the lowest faucet – which is usually the one inside the basement – and let the water drain. This will allow air to enter the air chambers.
  • Turn off the lowest faucet, and turn on the main water valve.
  • Allow the top faucet to run until it stops sputtering. Turn it off once this happens, and you’re done.

If your home is built after the ‘60s, you likely have water hammer arrestors. This is a modern solution with the same purpose as air chambers. They are spring-loaded and they are rarely faulty. Because of that, if you hear banging pipes when water is not running, you may not have these arrestors properly installed. To fix this, you need to contact a professional, as this requires some heavy-duty plumbing.

2. Random Banging Noise Throughout the Day

If you have banging pipes at random, the likely cause is sediment buildup inside the water heater. This can even be one of the water heater failure signs.

This noise is caused by steam bubbles that are escaping the deposit at the bottom of the tank. Think of it as bubbles when the water is boiling. It can be loud enough to appear as if the noise is coming from the walls.

Sediment build-up can be prevented by flushing your water heater regularly. This will clean up the minerals that deposit on the heating element, which is located at the bottom of the tank.

The water that goes through your pipes isn’t pure. It contains many minerals, either to keep the water sterile from the bacteria and toxic substances, or it collects them as it’s passing through the pipes.

To flush the tank by yourself, follow these steps:

  • Use heavy-duty gloves so you don’t get burned!
  • Turn off your water heater. If you have a gas one, switch the temperature settings to PILOT. For an electric water heater, simply turn it off at the circuit breaker.
  • Turn off the cold water valve, so not even the cold water can enter the water heater.
  • Let the heater cool for up to half an hour. Don’t attempt to flush it sooner, or you might get burned.
  • Take a garden hose and connect it to the drain valve.
  • Place the other end of the garden hose somewhere where the water and the sediment deposits can be safely drained.
  • Open a hot water faucet in a tub or a sink, so the vacuum doesn’t form.
  • Open the drain valve. To do so, turn a slot located on the valve.
  • Pull the tab out on your pressure relief valve.
  • Allow the water to drain entirely. Don’t worry if you don’t see any sediment coming out.
  • Turn on the cold water valve to flush out any existing sediment.
  • Once the water that runs out is clean again, close the drain valve. This will allow the cold water to fill the water heater’s tank.
  • Turn the heating element back on.

You should flush your tank this way at least once a year. [2]

The Bottom Line

Having banging pipes when water is not running isn’t just annoying. It can also be an indication that something is seriously wrong with your plumbing. If you don’t deal with it as soon as possible, you might end up with a leak in your hands.

If you are unsure whether you can follow the steps we’ve listed above, you should contact a professional plumber for help. There isn’t any shame in not knowing how to something on your own. A professional can ensure your problem is solved.