Pipes & water supply

Water hammer arrestor failed or missing

If banging pipes return after previously being fixed, an existing arrestor may have failed internally, or one may be needed where it was never installed.

Difficulty
Easy
Time
15–30 minutes
DIY cost
$10–$35
Pro cost
$100–$300

Symptoms

  • Banging pipes that previously stopped have returned
  • No visible arrestor at supply lines for washing machines or fast-closing valves
  • Noise pattern matches classic water hammer (bang when a valve shuts quickly)
  • Arrestor, if visible, may look corroded

Likely causes

  • CommonArrestor's internal air chamber or piston failed over timeThese devices absorb shock using a sealed air cushion or spring-loaded piston, which can wear out after years of use.
  • CommonArrestor never installed for that specific fixture or applianceOlder homes and some renovations skip these devices even where fast-closing valves are present.
  • PossibleArrestor undersized for the water hammer severity at that locationA basic model may not fully absorb shock from very high pressure or a particularly aggressive valve.
  • Less commonCorrosion or physical damage to the arrestor itselfAge and water quality can corrode the arrestor's internal components independent of normal wear.

What to do

  1. Identify the fixture or appliance where banging occurs and check its supply line connections for an existing arrestor.
  2. If one exists and the noise has returned, unscrew and replace it with a new one of the same or a higher capacity rating.
  3. If none exists, install one between the shutoff valve and the supply hose for that fixture, following the product's instructions.
  4. For multiple recurring hammer points throughout the house, consider having a plumber install larger capacity arrestors at the main lines instead of individual fixtures.
  5. Check your home's water pressure as well, since persistently high pressure can overwhelm even a properly sized arrestor.
  6. Test by running the fixture or appliance through its normal cycle and listening for the bang.
  7. Replace any other visibly corroded arrestors found during the inspection, since they tend to fail around the same age.

Tools and parts

  • Wrench
Water hammer arrestorSearch: “water hammer arrestor replacement”

When to call a pro

Call a plumber for whole-house arrestor installation at the main lines if individual fixture arrestors aren't resolving widespread banging.

Safety

Generally low risk

Generally low risk for a careful person. Stop if anything looks different from what this guide describes.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.