How to Fix Water Hammer in Pipes

By
Lee Wallender
Lee Wallender
Lee Wallender

Lee has over two decades of hands-on experience remodeling, fixing, and improving homes, and has been providing home improvement advice for over 13 years.

Learn more about The Spruce's Editorial Process
Updated on 12/14/22
Reviewed by
Richard Epstein
Richard Epstein
Reviewed by Richard Epstein
Richard Epstein is a licensed master plumber with over 40 years experience in residential and commercial plumbing. He specializes in estimating as well as design and engineering for plumbing systems, and he works for one of New York's largest union plumbing construction companies.
Learn more about The Spruce's Review Board
Fact checked by
Sarah Scott
SS
Fact checked by Sarah Scott
Sarah Scott is a fact-checker and researcher who has worked in the custom home building industry in sales, marketing, and design.
Learn more about The Spruce's Editorial Process
Fixed pipes under sink with water hammer issues

The Spruce / Kevin Norris

Project Overview
  • Working Time: 20 - 30 mins
  • Total Time: 20 - 30 mins
  • Skill Level: Intermediate
  • Estimated Cost: $20 to $40

Water hammer is a common plumbing problem. It's an annoying sound, a loud "bang" that can be quite startling. And while you may want to wish it away as simply one of those harmless everyday sounds, it can eventually damage your plumbing system. Learning the basics of water hammer and fixing it can save you thousands of dollars in repairs down the road.

How You Know If You Have Water Hammer

Water hammer, or hydraulic shock, is both a sound and a sensation. You'll be shutting off a faucet when a quite audible bang vibrates up the pipes. Because sound is vibration, it's often strong enough so that you can feel it under your hand as you hold the faucet or the handle. You may even see the faucet slightly jump.

The shock of water hammer can even cause dishes and glasses in cabinets to vibrate. You may also hear the sound resonate within the house's inner structure.

What Causes Water Hammer

Water hammer happens because water is shut off quickly. While sink, tub, and shower faucets can cause water hammer, more often clothes washers and dishwashers can cause water hammer because they can shut off water faster than by hand. These appliances use solenoid valves, which can close off in as fast as 30 milliseconds.

The alarming sound is caused by the sudden stoppage of water flow. This causes the water supply pipes to bang against studs, joists, beams, or even against other water supply or drain pipes.

Tip

Although you don't hear it as loudly, water hammer can also be an issue with plastic water supply pipes, such as CPCV and PEX. Pipe and water damage is still a potential danger. If you have open areas where plastic plumbing pipes are exposed, watch the pipes for signs of movement and flexing when someone abruptly turns off faucets. Water hammer in plastic pipes also calls for remedy.

Methods for Fixing Water Hammer

Air Chambers

If you've ever seen mysterious lengths of 12-inch capped pipe extending from the supply pipes, these are air chambers meant to quiet water hammer. Filled with air, each pipe acts as a shock absorber for the water that comes to a sudden halt. Air compresses; water does not. This means that the air in the chamber acts as a cushion for the water.

This simple solution requires advanced plumbing skills for installation. Plus, air chambers can fill with water over time, so the pipes may occasionally need to be drained.

Tip

Water supply pipes must be properly secured. It's always a great idea to replace broken or loose straps as a part of a proper house maintenance schedule. When possible, replace with cushioned pipe clamps made of steel and soft EPDM rubber.

Water Hammer Arresters

A water hammer arrester improves on the idea of the air chamber by adding a chamber filled with gas or air that's sealed with a piston or a diaphragm. The diaphragm separates the water and the gas or air.

What Is a Diaphragm?

In plumbing, a diaphragm is a flexible disc that responds to pressure to form a seal, stopping water flow. Diaphragms are often made of various kinds of rubber, along with other materials.


A water hammer arrester is often spliced into the point where the water supply tube/hose meets up with a shutoff valve. With this method, no pipes need to be cut or sweated back together. Push-fit water arresters are also available.

Look for water arresters that are combined with a valve. Sometimes, space may be an issue, so be sure to purchase a water arrester that fits the space.

Water-Pressure Regulators

Water hammer can also occur when the overall pressure of the main water pipe entering the building is too high. Normal water pressure runs between 40 and 60 psi (pounds per square inch), and above this, the high pressure could be the source of water hammer. Very high pressure above 80 psi can also damage appliances.

In this case, installing a water-pressure regulator can solve water hammer issues. Where possible, it's better to install the water-pressure regulator at the location where the main water supply enters the home rather than installing multiple air chambers, because the device also protects dishwashers, toilets, and other appliances and fixtures against high water pressure.

Start by testing water pressure to verify that it is higher than normal. After installing the water-pressure regulator at the main water supply entry, adjust the regulator to a pressure below 50 psi.

Featured Video

What You'll Need

Equipment / Tools

  • Bucket or towel
  • Tongue-and-groove pliers or adjustable wrench
  • Old towels

Materials

  • Water hammer arrester
  • Plumber's thread seal tape

Instructions

Materials and tools to fix water hammer issues in pipes

The Spruce / Kevin Norris

How to Fix Water Hammer With a Water Hammer Arrester

  1. Turn off the Water

    Shut off the water to the clothes washer, dishwasher, or other areas that experience water hammer. The device will usually have a shutoff valve that can be turned clockwise to shut off the water. In some cases, you may find an intermediary shutoff valve farther up the line. For installing multiple water hammer arresters, you may want to shut off the home's entire water supply.

    Tip

    The washing machine will have two shutoff valves, one for hot and another for cold. The dishwasher will have one shutoff valve for hot.


    Water pipe turned off with shutoff valve

    The Spruce / Kevin Norris

  2. Disconnect the Hoses

    Use a basin to catch spilled water from disconnecting the water hoses. Have a few old towels nearby, too. Use tongue-and-groove pliers or an adjustable wrench to turn the hose fittings loose.

    Water hoses disconnected from valves with wrench

    The Spruce / Kevin Norris

  3. Install the Water Hammer Arrester

    There are a few ways to do this.

    Threaded: For threaded water hammer arresters, thread the device onto each valve or inlet. Turn the female fitting clockwise by hand, then tighten with the pliers.

    Tip

    If using a threaded water hammer arrester, for a tighter fit, you can wrap the male end of each shutoff valve or water inlet with thread seal tape or Teflon tape before threading the arrester on. Wrap the tape tightly three or four times clockwise. Wrap any male threads on the water hammer arrester with tape, too.

    Compression: For compression fittings, slide the compression ring against the valve, then thread on the compression nut and tighten.

    Push-Fit: Push-fit water hammer arresters need no tools for installation (though removal does require a small plastic tool). Clean copper tubes of burrs. Make sure that all cuts are square. Push the fitting firmly onto the pipe.

    Water hammer arrestor threaded unto valve

    The Spruce / Kevin Norris

  4. Connect the Supply Tube or Hoses

    Use the pliers or the wrench to connect the water supply tube or hose to the water hammer arrester. Tighten the connection.

    Water supply hoses connected to water hammer arrestor

    The Spruce / Kevin Norris

  5. Turn on the Water

    Slowly turn on the water supply by turning the shutoff valve counterclockwise. If you shut off the water to the entire house, faucets may sputter before water begins running freely again. Use a flashlight to visually inspect the connections for leaks. Run every appliance on a water hammer arrester on one test cycle.

    Water supply turned on by moving shutoff valve counterclockwise

    The Spruce / Kevin Norris

Article Sources
The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. Residential Plumbing Overview. National Association of Certified Home Inspectors.

  2. Water Pressure. Padre Dam Municipal Water District.