How to Install a Water Hammer Arrestor
Updated February 25, 2026
Stop banging pipes by installing a water hammer arrestor at the fixture causing the noise -- a 15-minute fix that protects pipes from pressure shock damage.
Overview
Water hammer is the loud bang or thud you hear when a valve closes suddenly -- the dishwasher finishing a fill cycle, the washing machine switching between cycles, or a quick-close faucet snapping shut. The noise is a pressure shockwave traveling through the pipes at 4,000+ feet per second. Over time, these shockwaves loosen pipe joints, damage appliance valves, and can split copper fittings. A water hammer arrestor is a small sealed chamber with a piston or bellows that absorbs the shockwave before it travels through the plumbing. Install one at each fixture that causes the bang.
What You'll Need
Safety First
- Turn off the water supply to the fixture before installing the arrestor. You are adding a tee fitting to the supply line, which requires disconnecting a connection.
- Water hammer arrestors are sealed -- they do not need draining or maintenance. Do not attempt to open or service one.
Step-by-Step Instructions
- Identify the Source Fixture
Water hammer occurs at the fixture where the valve closes fastest. Common culprits: washing machine (solenoid valves snap shut between cycles), dishwasher (fast-acting fill valve), ice maker (small solenoid with fast close), and single-lever faucets (quick shutoff). Run each suspect fixture and listen for the bang. The arrestor goes at that fixture's supply connection, not at a random point in the plumbing.
Tip: If the bang happens when the washing machine stops filling, you need arrestors on BOTH the hot and cold supply hoses at the washing machine. Both valves close simultaneously. - Choose the Right Arrestor
Residential arrestors come in sizes AA (smallest, for single fixtures) through F (largest, for multiple fixtures on a branch). For a washing machine: type AA or A, one on each supply. For a dishwasher: type AA. For a faucet: type AA. Sioux Chief mini-rester ($10-$15) and Watts series 15 ($12-$20) are the most common residential models. They thread onto standard 3/4-inch hose connections (washing machine) or 3/8-inch or 1/2-inch supply lines (under sinks).
Tip: For washing machines, the easiest installation uses arrestors that thread directly onto the hose bib (the valve on the wall where the washing machine hoses connect). No pipe cutting needed. - Install at the Washing Machine (Most Common)
Turn off both hot and cold supply valves. Disconnect the washing machine hoses from the wall valves. Thread the arrestor onto the valve outlet (where the hose was). Thread the washing machine hose onto the arrestor. The arrestor sits between the valve and the hose. The internal piston faces up. Tighten each connection hand-tight plus a quarter turn with pliers. Turn on both valves. Check for leaks. Run the washing machine through a cycle and listen -- the banging should be gone.
Tip: The arrestor adds about 4 inches of length between the valve and the hose. Make sure there is enough space behind the washing machine to accommodate the extra length. If not, use a shorter washing machine hose. - Install Under a Sink (For Dishwashers and Faucets)
Turn off the supply valve under the sink. Disconnect the supply line from the valve. Install a tee adapter on the valve outlet. Connect the supply line to one port of the tee. Thread the arrestor onto the other port (pointing upward). Tighten all connections. Turn on the valve and check for leaks. If using a push-fit tee (SharkBite), no tools needed -- push the pipes in and thread the arrestor onto the branch port.
Tip: The arrestor must be installed as close to the valve as possible -- ideally at the supply connection, not 10 feet upstream. The further from the source, the less effective it is at absorbing the shockwave.
Pro Tips
- Old-style air chambers (vertical dead-end pipe stubs) served the same purpose as modern arrestors but waterlog over time and stop working. If your home has air chambers and the hammer has returned, the chambers are waterlogged. Modern piston or bellows arrestors are sealed and never waterlog.
- If water hammer occurs at multiple fixtures, the house may have excessively high water pressure (above 80 PSI). A pressure reducing valve (PRV) at the main reduces pressure system-wide and often eliminates hammer without individual arrestors. Check your pressure first.
- Thermal expansion can mimic water hammer. If you hear a bang when the water heater finishes heating (not when a valve closes), the cause is thermal expansion -- the heated water expands with nowhere to go. An expansion tank ($40-$100) on the cold inlet to the water heater solves this.
- Water hammer arrestors have a lifespan of 10-20 years. If yours stop working, they are likely due for replacement. They are sealed units -- replacement, not repair.
- Loose pipe supports (straps, hangers) amplify the noise from water hammer. Even without an arrestor, securing loose pipes to framing with pipe clamps every 4-6 feet reduces the audible bang significantly.
When to Call a Pro
Call a plumber if water hammer persists after installing arrestors at the source fixtures (may indicate excessively high water pressure, thermal expansion, or a more complex hydraulic issue), if you need a pressure reducing valve installed on the main line, or if the hammer is caused by a failed check valve or PRV that is creating hydraulic instability.
Frequently Asked Questions
When should I call a plumber to install a water hammer arrestor?
Call a plumber if water hammer persists after installing arrestors at the source fixtures (may indicate excessively high water pressure, thermal expansion, or a more complex hydraulic issue), if you need a pressure reducing valve installed on the main line, or if the hammer is caused by a failed check valve or PRV that is creating hydraulic instability.
What are some expert tips to install a water hammer arrestor?
Old-style air chambers (vertical dead-end pipe stubs) served the same purpose as modern arrestors but waterlog over time and stop working. If your home has air chambers and the hammer has returned, the chambers are waterlogged. Modern piston or bellows arrestors are sealed and never waterlog. If water hammer occurs at multiple fixtures, the house may have excessively high water pressure (above 80 PSI). A pressure reducing valve (PRV) at the main reduces pressure system-wide and often eliminates hammer without individual arrestors. Check your pressure first. Thermal expansion can mimic water hammer. If you hear a bang when the water heater finishes heating (not when a valve closes), the cause is thermal expansion -- the heated water expands with nowhere to go. An expansion tank ($40-$100) on the cold inlet to the water heater solves this. Water hammer arrestors have a lifespan of 10-20 years. If yours stop working, they are likely due for replacement. They are sealed units -- replacement, not repair. Loose pipe supports (straps, hangers) amplify the noise from water hammer. Even without an arrestor, securing loose pipes to framing with pipe clamps every 4-6 feet reduces the audible bang significantly.
What tools do I need to install a water hammer arrestor?
You will need: Water hammer arrestor ($10-$25 each, sized to the fixture), Adjustable wrench or channel-lock pliers (for supply line connections), Teflon tape (for threaded connections), Tee adapter (for under-sink installations where a branch connection is needed), Bucket and towel (for catching residual water when disconnecting supply lines).
When should I call a professional instead of doing this myself?
Call a plumber if water hammer persists after installing arrestors at the source fixtures (may indicate excessively high water pressure, thermal expansion, or a more complex hydraulic issue), if you need a pressure reducing valve installed on the main line, or if the hammer is caused by a failed check valve or PRV that is creating hydraulic instability.
How difficult is this project?
This project is rated easy. Most homeowners with basic tools can complete it.
How long does this take?
Plan for approximately 15 - 30 minutes per arrestor. First-timers may need extra time.
How much will this cost?
The estimated cost is $10 - $25 per arrestor. Costs vary by location and materials chosen.