Symptoms
- Loud thud or bang in the walls right when water is shut off
- Noise happens with other fixtures too, not just the shower
- Sound seems to come from inside the wall near the valve
- Pipes may visibly shake briefly
Likely causes
- CommonMissing or failed water hammer arrestorThese small devices absorb the shock of stopping water flow, and many older homes never had one installed.
- CommonLoose pipes not properly strapped or securedPipes that can move slightly within walls or floor joists amplify the banging sound.
- PossibleHigh water pressure throughout the houseExcess pressure makes the sudden stop of flow more forceful and the resulting bang louder.
- PossibleAir chambers (older-style hammer prevention) waterloggedOlder homes used vertical air-filled pipe sections instead of arrestors, and these can fill with water over time, losing their cushioning effect.
What to do
- Note if the banging happens with other fixtures (like a washing machine solenoid valve) or just the shower.
- Check your home's water pressure with a gauge on an outdoor spigot; above 80 psi is high and worsens hammer.
- If pressure is high, consider having a pressure-reducing valve installed at the main line.
- For an isolated fixture, a hammer arrestor can often be installed at the shower valve's supply line, though this may require opening the wall.
- For homes with old air chambers, draining the system fully (shut off main, open all faucets) can sometimes restore trapped air and quiet the noise temporarily.
- Check for loose pipes in accessible areas like a basement and add pipe straps or cushioned clamps where they contact framing.
- If the noise persists after these steps, a plumber can install arrestors at the specific problem fixtures.
Tools and parts
- Water pressure gauge
- Pipe straps (if accessible pipes are loose)
Water hammer arrestorSearch: “water hammer arrestor”
When to call a pro
Call a plumber if the banging is loud, frequent, or the fix requires accessing pipes inside walls or under slabs.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.