Quick Answer:
If an outdoor spigot makes a hammering or banging noise when you close it, it’s usually water hammer (a sudden pressure spike) or a loose pipe/support near the valve. Test by closing the spigot quickly then slowly and listening inside the wall to help locate the noise. Many cases are simple to diagnose and may only need a clamp or a pressure arrestor; persistent bangs or leaks mean call a plumber.
Why This Happens
When flowing water is stopped suddenly, the moving column of water has momentum and creates a pressure spike. That spike can make pipes knock against framing or send a loud bang through the wall. Common causes:
- Water hammer from sudden shutoff (most common when the valve is closed fast).
- Loose pipe supports or straps allowing movement when pressure changes.
- Worn valve seat, packing, or washer that causes abrupt closure or chattering.
- High system pressure or a partially closed isolation valve creating turbulence.
- Frozen or partially frozen sections can also change flow and create noise.
Step-by-Step What to Do
1. Reproduce the sound safely
Go outside with someone inside the house. Close the spigot quickly then slowly to see whether the noise changes. This helps confirm the spigot is the trigger and whether speed of closure matters.
2. Listen inside the wall to find the bang location
Have the person inside place their ear near the wall behind the spigot and along nearby studs or the ceiling. Move along the wall while you operate the spigot. Identifying the general location helps decide if the pipe is free to move or hitting framing.
3. Check for loose piping and supports
With the main water off (if you can safely do so), inspect where the pipe enters the house. Look for loose straps, hangers, or a spigot mounting screw that’s loose. Tighten loose supports but avoid over-tightening copper or plastic pipe—use padded clamps if possible.
4. Reduce pressure and relieve trapped air
Shut off the outdoor spigot’s shutoff inside the house (if present) or the main shutoff. Open several faucets to drain pressure. Trapped pressure or air can make banging worse; draining the line can help determine if the problem is pressure-related.
5. Inspect the spigot itself
Turn the spigot open and closed slowly while watching for chatter or irregular resistance. If it doesn’t close smoothly or leaks when closed, the internal seat or washer may be failing. If the unit won’t shut off fully, refer to Outdoor Spigot Won’t Turn Off Completely for more on diagnosis and repair options.
6. Test fixes and re-check noise
After securing pipes and easing pressure, test the spigot again (both quick and slow closure). If you still hear the bang inside the wall, especially in the same spot, it may be a case of the spigot causing knocks on framing—see guidance related to Outdoor Spigot Knocks Pipes Inside the Wall.
7. Consider a water hammer arrestor or pressure adjustment
If the cause is water hammer and supports are solid, a plumber can install a water hammer arrestor or check system pressure and add pressure-reducing equipment if needed.
What Not to Do
- Do not slam spigot closed repeatedly. Repeated slamming increases pressure spikes and can damage valves and pipes.
- Don’t tear open drywall without first shutting off water and confirming the exact location of the problem.
- Avoid makeshift metal clamps or forcing quick repairs on corroded fittings—this can cause leaks or breaks.
When to Call a Professional
- There is ongoing loud banging after basic checks and securing the pipe.
- You find or suspect a leak, moisture inside the wall, water damage, or mold.
- The spigot won’t close properly or you’re unsure where the shutoff is located.
- Work needed involves soldering, cutting pipe, or opening walls you’re not prepared to repair.
Safety Notes
- Turn off the main shutoff before doing any work that exposes piping. Drain lines before loosening fittings.
- In cold weather, be cautious of frozen pipe sections—forcing frozen fittings can cause breakage.
- If you find active leaks behind drywall, stop and call a plumber; water inside walls can cause rapid secondary damage.
Common Homeowner Questions
- Why does it only happen when the spigot is closed? — Sudden shutoff causes a pressure spike that moves the water column and can make pipes knock against framing.
- Will this damage the spigot or pipes? — Repeated pressure spikes can wear valve seats, packing, and joints, and may eventually cause leaks.
- Is there a simple temporary fix? — Securing loose pipe supports and closing the spigot more slowly can reduce or stop the noise; permanent fixes may require a plumber.