Quick Answer:
If an outdoor spigot is knocking or rattling pipes inside a wall, it usually means a pipe is loose, contacting the stud or other surface, or the spigot/valve is vibrating when water flows. Open the wall access panel to look for loose straps or obvious damage, then run the spigot briefly while feeling the pipes to find the vibration source. Small movement can sometimes be secured; significant damage or active leaks should be handled by a plumber.
Why This Happens
- Loose supports: Pipes should be strapped to framing. If a strap breaks or was never installed, the pipe can bang against wood when water flows.
- Water hammer and vibration: Sudden changes in flow or a worn valve can make pipes vibrate or produce knocking sounds.
- Thermal expansion: Metal pipes expand and contract, which can shift them into contact with framing if they’re not properly cushioned.
- Corrosion or wear at the spigot or fittings can let the faucet vibrate and transfer that motion into the wall. If you notice staining or buildup near threads, see why a spigot can rust. You can also learn more about white or cloudy water with Outdoor spigot water is milky at startup if that’s happening alongside the noise.
Step-by-Step What to Do
1. Prepare and protect the area
- Clear furniture and belongings near the access panel and outside spigot.
- Have a flashlight, gloves, and a towel ready for small drips.
2. Open the wall access panel
- Locate the indoor access panel or closet that lines up with the outdoor spigot and remove the cover. This is the panel you were instructed to use for winterizing in many homes.
- Look for loose pipe straps, missing insulation, obvious movement, or water stains on framing or drywall.
3. Run the spigot and feel the pipe to find the vibration
- With one person at the spigot and one at the access panel, open the spigot slowly and then fully for a short time while you place a hand on the pipe inside the wall.
- Note where the vibration or knocking is strongest (near a fitting, an unsupported run, or where the pipe contacts framing).
- If you detect an active leak while doing this, shut the spigot off immediately and close the nearest shutoff valve. If you cannot stop the flow, turn off the home’s main water supply and call a professional.
4. Make small, safe adjustments if comfortable
- If a pipe strap screw is loose and accessible, tighten it a turn or two to secure the pipe. Do not over-tighten—metal pipes can be damaged by excessive torque.
- Temporary cushioning (a small strip of rubber or felt) behind a rubbing spot can reduce noise until a proper repair is made.
- If you find corrosion or broken fittings, stop and call a plumber—those issues can lead to leaks if mishandled.
5. Monitor after the check
- Run the spigot again after any adjustment to confirm the knocking is reduced.
- Keep an eye on the area for a few days for new stains, drips, or continued noise.
What Not to Do
- Do not hammer pipes back into place. This can dent or crack the pipe, loosen fittings, and create leaks.
- Do not cut or solder plumbing unless you are trained and have shut the water supply off properly.
- Do not ignore active leaks or visible water damage—small leaks can become big problems quickly.
When to Call a Professional
- There’s an active leak you cannot stop or that leaves water stains on the wall or ceiling.
- Knocking continues after you’ve tightened accessible straps or added temporary cushioning.
- You find corrosion near the spigot or fittings, or the spigot itself is loose at the exterior wall. For issues like a rusted connection, see guidance on Outdoor spigot rusts around threads.
- Walls need to be opened beyond the access panel or insulation and wiring are involved—these situations need a licensed plumber or contractor.
Safety Notes
- Turn off the water supply if you find an uncontrollable leak.
- Be cautious of electrical wiring in the access area—do not pry or cut anything behind the panel.
- Wear gloves and eye protection if you are handling rusty fittings or insulation.
- If you suspect frozen or burst pipes in cold weather, shut off the water and call a professional—thawing or repairs can be risky without experience.
Common Homeowner Questions
- Why does the noise only happen when the spigot is on?
Because flow or valve movement causes the pipe to vibrate or strike framing; no flow means no force to move the pipe. - Can I fix loose pipe straps myself?
Yes, if the strap and screw are accessible and you’re comfortable with basic tools—tighten carefully and avoid over-torquing. - Is knocking a sign the pipe is about to burst?
Not always, but persistent knocking with signs of corrosion or wetness warrants an inspection by a plumber.