Learning, Hammer,

Where are Water Hammer Arrestors Required?

By the end of this article, you’ll know where to install water hammer arrestors.

Knowing when and where water hammer arrestors are required will get you out of many messy situations. These devices can absorb the excessive pressure created by water. Water hammer arrestors are excellent protection for pipes. But you should know exactly where to install them.

In general, you should install water hammer arrestors on your quick-closing valves. It could be on dishwashers, ice makers, washing machines, or coffee machines. If a particular valve makes too much noise while you close it, installing a water hammer arrestor might be a good idea.

Things You Should Know About Water Hammer Arrestors

Whatever the type of your home, you might have lots of quick closing valves. But have you ever thought about what happens when you close a faucet quickly?

This process is directly connected with the water hammer arrestors.

water flow diagram in a pipe
Video | Got2Learn

When you close a valve, it shuts up the water supply immediately. But due to this sudden stop, the water bounces back to its original path. This process creates unwanted pressure and needs to be released in some manner.

water pipe with close valve
Video | Got2Learn

Otherwise, this process will damage your pipes and make some unusual noises.

water pipe with o-rings
Video | Got2Learn

To avoid all of this, plumbers use water hammer arrestors. The device has a sealed chamber, polypropylene pistons, and two sealing O-rings. These O-rings sealed the air chamber properly. Because of that, the water won’t go inside the air chamber. Examine the above image for better understanding.

Quick Tip: You can place the hammer arrestors vertically or horizontally.

Therefore, the excessive pressure will be absorbed by the water hammer arrestor with the help of the polypropylene pistons.

Where are Water Hammer Arrestors Required

water flowing on sink
Video | Got2Learn

You’ll have to install a water hammer arrestor on all of your fast-closing valves, and it will prevent any unusual noise. At the same time, the pipe won’t expose to unwanted pressure. So they will last longer.

For instance, use hammer arrestors for faucets, washing machines, ice makers, dishwashers, coffee makers, etc.

Why Don’t Old Fashioned Water Hammer Arrestors Work?

air level before
Video | Got2Learn

In the past, plumbers used hammer arrestors in quick-closing valves. But there was a major issue in those water hammer arrestors. The air chamber wasn’t sealed properly. Hence, the air chamber was covered with water after a week or two. This was a major issue in the old hammer arrestors.

But, nowadays, these devices come with two O-rings that can seal the air chamber. So, you don’t have to maintain the hammer arrestor often.

Quick Tip: When the air chamber was flooded, plumbers drained the water and then filled the air into the chamber. This process was done regularly.

Do All Pipes Need Water Hammer Arrestors?

According to the NC guideline, using plastic pipes, you won’t need water hammer arrestors (PEX and PVC). This is why you cannot locate water hammer arrestors in some coffee machines and ice makers.

Quick Tip: Even though metal pipes are most likely to cause trouble due to water hammers, some plastic pipes also can expose to vibration. So, use hammer arrestors whenever you need them.

What is Water Hammering?

The knocking noise that water pipes make is known as water hammering. This situation mostly occurs in quick closing valves. Using a hammer arrestor is the solution for this matter.

Types of Water Hammer Arrestors

When it comes to hammer arrestors, there are two types.

  • Hammer arrestors with pistons
  • Hammer arrestor without pistons

Depending on your situation, you can choose either one of them. However, a non-piston hammer arrestor can cause problems to the air chamber. This could be a problem in the long run, and the hammer arrestor might become obsolete.

Installing Water Hammer Arrestors

If you are experiencing an unusual noise from your pipes while closing the valve, it might be time to install a water hammer arrestor.

damaged pipeline releasing water
Video | Got2Learn

The sudden stop of the water flowing momentum can damage your pipelines permanently. So, it is wise to take necessary action before everything falls apart.

After installing the water hammer arrestor, the device will absorb excessive pressure in the pipe.

With that in mind, here’s how to install a hammer arrestor at your home.

Step 1 – Gather the Required Tools

First and foremost, gather the following tools for your home DIY project. (1)

  • Pliers
  • Adjustable wrench
  • Pipe wrench
  • Suitable hammer arrestor

Step 2 – Cut off Water Supply

Connecting the hammer arrestor while the water is flowing will be impossible. So, cut off the main water supply. (2)

Don’t Forget: Remember to drain any remaining water in the pipeline. Open the nearest faucet and let the water go out.

Step 3 – Disconnect the Supply Line

Disconnect the supply line from the valve.

Step 4 – Connect the Hammer Arrestor

Next, connect the hammer arrestor to the valve. If needed, use the wrench.

Step 5 – Connect the Supply Line

Now, reconnect the supply line to the hammer arrestor. Use the necessary tools for this step. Finally, open the main water supply line.

If you follow the above process correctly, you won’t hear any clanging and banging from your pipes.

Where is the Perfect Location to Install a Water Hammer Arrestor?

This is a question most people ask during my plumbing projects. However, the answer is not that complicated.

You should install the hammer arrestor close to where the water hammering occurs. For instance, I usually install hammer arrestors close to bents and joints. Most of the time, bents and joints show signs of water hammering. Especially if the connection is bad, the joints will leak over time. Other than that, there is no specific location.


Should I Use a Hammer Arrestor in the Average Household?

Yes. Whatever the size of the residential piping system, it is wise to use hammer arrestors. If the pipes are dealing with excessive water pressure, they might show signs of water hammering. For instance, the pipes might make unusual noises or shows signs of excessive shock, and this shock might cause leaks in your piping system.

Hence, installing water hammer arrestors is a must. It will prevent noise and shock. Apart from that, you’ll be able to use your piping system without any issues for a long time. Install hammer arrestors in all fast-closing valves in your household.

Do I Have to Install a Water Hammer Arrestor on Plastic Pipes?

The answer to this question is a little complicated. According to the NC guideline, installing a hammer arrestor on plastic pipes such as PEX and PVC is unnecessary. But keep in mind that even plastic pipes can get exposed to vibration. Hence, installing a hammer arrestor on a plastic pipe is not the worst.

Take a look at some of our related articles below.

(1) DIY project – https://www.bobvila.com/articles/diy-home-projects/
(2) water supply – https://www.britannica.com/science/water-supply

Video References


SharkBite Plumbing

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About Sam Orlovsky

AvatarCertifications: B.E.E.
Education: University Of Denver - Electric Engineering
Lives In: Denver Colorado

Electrical engineering is my passion, and I’ve been in the industry for over 20 years. This gives me a unique ability to give you expert home improvement and DIY recommendations. I’m not only an electrician, but I also like machinery and anything to do with carpentry. One of my career paths started as a general handyman, so I also have a lot of experience with home improvement I love to share.

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