How to Fix Water Hammer in Your Plumbing System

  • 01 of 02

    How to Fix Water Hammer

    water hammer arrestor
    Sioux Chief

    It happens when you do nothing more than quickly shut off a faucet.

    BANG! Water hammer. It sounds like a shock wave just went through your pipes!

    Well, in fact, one just did. Water hammer can damage your plumbing system. The shock wave that created the water hammer is traveling at thousands of feet per second and exerts pressures at hundreds of pounds per inch. So just what is water hammer?

    Let's take a look at what it is and how to solve it.

    Water Hammer (hydraulic shock) is by far the loudest and...MORE most common plumbing noise problem in the home. You hear it in a home having high water flow rates (around 10 feet per second) when a faucet or water valve is shut off quickly.

    Older homes have (or should have) what is called an "air chamber" located on each hot and cold water line at or near each faucet or water inlet valve. The purpose of the air chamber is to act as a shock absorber for water when it is flowing at high speed under pressure. Since air compresses (it's a vapor) and water doesn't, the air chamber allows the water a place to temporarily expand into and softens the blow of the water shock wave when the faucet is turned off quickly.

    Air chambers are often fabricated on-site by the plumber and installed at the faucet's water supply. They typically consist of a vertical length of capped pipe about 12" long or longer and are the same diameter as the water supply pipe. The problem with these things is that they are sometimes made too short and undersized and eventually fill up with water and you have no more shock absorber. The result? Water hammer. If you have a water filled air chamber it can be easily fixed by draining and recharging the plumbing system.

    A better solution to alleviate the problem is to have a mechanical or engineered water hammer arrestor installed. These mechanical plumbing devices are charged with air or gas and will not fail like typical air chambers.

    Compare Prices Water Hammer Air Chamber

    The ultimate solution? Design the water supply system properly in the first place with larger supply lines so that it has about a 5 feet per second water flow rate.

    Continue to 2 of 2 below.
  • 02 of 02

    Draining and Recharging the Plumbing System

    faucet draining
    © Phattman -

    Sometimes you need to drain the entire plumbing system in your home. If you have a water hammer problem and older style air chambers, then you need to learn how to drain the system so that air can refill the air chamber. Although draining the system will solve (or greatly reduce) your water hammer problem, the problem will come back as the water system is used. It may be a few months or it may be a year, but you'll have to do this again.

    To drain and recharge the water in your plumbing system...MORE follow the steps outlined in this tutorial: How to Drain Your Home's Plumbing System.