Why Does My Kitchen Faucet Thump?

When you turn off a kitchen faucet, the last thing most folks expect to hear is a thumping or banging noise. After all, you’re not standing next to a band performing a heart-pumping piece with an impressive bass, so why is your kitchen faucet thumping?

Generally, this stems from something called water hammer, which is a fairly common issue. We’re here to explain what it is, why it happens, and how to fix it, so continue reading to learn more!

Why Is My Faucet Making A Knocking Noise?

If your faucet makes a thumping noise when you turn the handle to turn off the water flow, there’s a good chance the culprit is water hammer. Although the sound might seem to stem from the faucet, it comes from the surrounding pipes.

As mentioned, it’s a fairly common issue that can happen in various parts of your home. You might hear the pipes throughout your home banging when the water is on, which usually points to water hammer as the culprit. Of course, this isn’t always the case, as other things can cause this noise, like high water pressure or loose pipes.

What Is Water Hammer?

Water hammer, also known as hydraulic shock, is a phenomenon that can occur in the plumbing throughout your home. Aside from the pipes in your home, it can also happen in nearly any piping system with valves that control the movement of liquids (or steam).

You’ll hear a bumping or knocking noise from the pipes when it happens. Sometimes, it can seem to come from the faucet, but the problem is usually beyond the fixture itself.

What Causes Water Hammer?

The knocking noise you hear when this phenomenon occurs happens because of a pressure surge in the plumbing. When the fluid in motion is forced to change direction or stop suddenly, it sends a high-pressure shockwave through the system, causing the knocking sound you hear.

Water hammer is common near water-using appliances and fixtures, including washing machines, toilets, and sometimes faucets. Since the water needs to stop abruptly due to the sudden lack of water demand, it doesn’t have anywhere to go. This creates the knocking or thumping as it hits the walls of the pipe.

While water hammer usually occurs when the water is off, it can occur when you turn your water on. For example, let’s say you turn on your kitchen faucet and hear a knocking noise immediately after. In this case, the faucet’s flow rate could be causing a resonant vibration that bounces the water from one side of the pipe to the other, causing the thumping noise.

Is Water Hammer Bad?

Although water hammer might not cause any issues immediately, it can lead to problems down the road. On top of creating an irritating noise, the vibrations and movement of the pipes during water hammer can lead to leaks in the plumbing. These leaks can create significant water damage and open the door to mold and mildew if left unchecked.

So, if you’re noticing water hammer in your home, it’s essential to get it taken care of sooner rather than later.

How Do I Fix A Thumping Kitchen Faucet?

There are several ways to approach a water hammer issue: drain the system or install an arrester. In some cases, draining the system might not work, so you’ll need to install an arrester as a solution to the issue.

Drain The System

Many modern residential homes feature vertical air chambers that are designed to prevent water hammer. The design functions based on the idea that the air in the pipes is compressible, so it should absorb the shock and force from the water as it abruptly changes its direction.

However, if these chambers fill with water, they can’t do their job effectively, leading to issues with water hammer. To correct this, you can drain the plumbing lines to “reset” the system. Follow these steps:

1. Turn off the water to your home at the main shut-off valve. This valve is often located where the main supply line enters your home.
2. Once the water is off, turn on the highest faucets in your home (if applicable).
3. Leave those faucets open, then move your way down through the house until you turn on all of the taps, moving from highest to lowest.
4. Keep the faucets open until all the water drains from the plumbing.
5. Once the water stops coming out of the faucets, reopen the main water shut-off valve to refill the pipes.

Install A water hammer arrestor

In some cases, draining and refilling the pipes won’t fix the problem. If that happens, you’ll probably need to install a water hammer arrestor. These cylinder-shaped devices are about 3-4 inches long and attach to the pipes.

The fitting features an air-filled chamber with a spring-loaded piston that absorbs the pressure from changes in direction. This effectively stops the pipes from banging. The installation process varies based on the location of the issue and the type of arrester you choose.

For example, you can solder the tee onto the pipes or fit it into place with a compression fitting. You’ll sometimes need to cut into the wall to access the pipe in question, so it can be a considerable project.

You can install these devices in various places, such as on the supply side of faucets, washing machines, or toilet shut-off valves. When you install the fitting, ensure you place it as close to the valve as possible.

How Much Does It Cost To Have A Water Hammer Arrestor Installed?

If you’re unfamiliar with the ins and outs of plumbing, it might be best to pass the project to a professional. Generally, you can expect to pay about $150 to have a plumber install the arrester.

Of course, costs may vary based on your location and the difficulty of the project (accessibility, leak repair, etc.), so you might pay slightly more or less for your installation.

Can I Install A Water Hammer Arrestor Myself?

Absolutely! Installing a water hammer arrestor yourself is entirely doable. If you’re completely unfamiliar with plumbing projects, you might want to outsource the project, but many homeowners can handle the installation without a hitch.

Bonus: DIYing the installation can save you quite a bit of money! The parts you’ll need usually cost less than $30 from your local home improvement or hardware store.