Quick Answer:
If you hear banging when no water is being used, it can be a pressure surge from the supply side, rapid valve action from the smart shutoff, or a trapped water-hammer condition in your plumbing. Note the exact times of each bang and whether the smart shutoff logged an event. If the pattern points to supply-side pressure swings, a plumber or your water utility can confirm and diagnose the issue safely.
Why This Happens
- Smart shutoff devices sometimes close valves quickly to stop flow; that rapid movement can create pressure spikes that sound like bangs.
- City water mains and neighborhood usage cycles can cause short pressure surges that travel into your house plumbing.
- Recent work on valves or service lines can leave the system sensitive — see Random hammer after installing backflow if this began after backflow or similar work.
- If curb box or street-side work occurred recently, those changes can show up as noise in your pipes — see Noise after curb stop work.
Step-by-Step What to Do
1. Record times and patterns
- Keep a log of each bang: note the clock time, how long it lasts, and how loud it is.
- Look for a repeating pattern (every hour, during morning usage, late night, etc.).
2. Check neighbors and your water utility
- Ask neighbors whether they hear similar noises or have had recent water-work notices.
- Contact your water utility to ask about scheduled work or known pressure events in your area.
3. Localize the sound
- Listen near the water heater and the main water entry point to the home to see where the bang is loudest—this helps determine whether it’s supply-side or inside-house piping.
- Walk the house while noting whether the sound is strongest by a particular fixture, line, or the main.
4. Isolate fixtures and devices
- Turn off all faucets, appliances, and automatic devices that use water. If the banging stops, re-enable them one at a time to find the source.
- Check the smart shutoff app or device logs for recent automatic closures that line up with the bangs.
5. Test the main shutoff (carefully)
- If comfortable doing so, briefly close the main shutoff to see if the noise stops; if it does, the issue is likely on the supply side rather than inside fixtures.
- Do not disable or bypass safety features while testing—only use the main shutoff as intended.
What Not to Do
- Don’t start opening walls or disabling safety devices; if bangs continue with no fixtures running, have a plumber evaluate pressure control components.
- Don’t attempt to adjust a pressure-reducing valve or smart shutoff internals unless you are trained and the system manufacturer recommends it.
When to Call a Professional
- Call a licensed plumber if the banging continues after you isolate fixtures and check the smart shutoff logs.
- If the noise occurs while all fixtures are off, or if you suspect high or fluctuating supply pressure, have a plumber inspect the pressure-reducing valve, backflow assemblies, and service connection. They can safely confirm whether the issue is supply-side or internal.
- Also call a pro if you notice leaking, visible pipe damage, or repeated events that risk stressing the plumbing.
Safety Notes
- Turn off the main shutoff only if you understand the location and operation—do not force valves that won’t move.
- Do not disable automatic shutoffs or other safety devices; they protect against leaks and flooding.
- If you must work near electrical panels or appliances while investigating, cut power first or keep hands and tools dry.
Common Homeowner Questions
- Is this likely to burst a pipe? Unlikely from a single bang, but repeated high-pressure events can strain fittings; have it checked if it continues.
- Can the smart shutoff cause this? Yes—rapid valve closures can create pressure spikes; check the device logs and settings.
- Should I call the water utility first? If multiple homes are affected or you suspect city work, yes—your utility can confirm supply-side events before a plumber visit.
For more related articles, see the Random Banging With No Water Running hub.