Quick Answer:
If you hear periodic banging in your plumbing when no water is being used, it’s most often caused by pressure surges (water hammer), thermal expansion near the water heater, or a failing pressure control device. Note the timing and location of the bangs. If the pattern points to supply-side issues or pressure control equipment, a plumber can confirm the cause safely and recommend repairs.
Why This Happens
Even when no taps are open, plumbing can experience sudden pressure changes. Common causes include:
- Water hammer from a valve or pump cycling sharply.
- Thermal expansion when the water heater fires and heats closed-volume systems.
- A failing pressure-reducing valve (PRV) or leaking check valve that lets the main supply surge.
- Municipal pressure changes or neighboring homes’ large draws that send short shocks through the lines.
These shocks can feel like hammering and, over time, may stress fittings and joints. Compare the pattern you record to notes about Banging after long periods of no use and Banging after PRV failure for clues about the likely source.
Step-by-Step What to Do
Step 1 — Record when each bang happens
Keep a short log for at least 24–48 hours. Note the exact time of each bang and whether it repeats at a similar interval. This timeline helps tell if the noise is tied to scheduled equipment (like a well pump) or to external supply changes.
Step 2 — Check whether neighbors or the utility are involved
- Ask a neighbor if they hear or experience the same noise or if they run large appliances at those times.
- Call your water utility or check local alerts to see if there were pressure adjustments or maintenance at the logged times.
Step 3 — Localize the sound
Walk through the house while the noise occurs, listening near the main water entry and the water heater. If it’s loudest near the water heater it may be thermal expansion or a heater-related valve; if it’s at the main entry or near a PRV, that points toward supply-side pressure events.
Step 4 — Reduce running equipment and observe
Turn off nonessential water-using appliances (dishwasher, washing machine) and see if the bangs continue. Make sure all faucets and fixtures are fully closed while you test. If the noise persists with nothing running, that increases the chance of a supply or pressure-control problem.
Step 5 — Gather useful information for a plumber
- Your time log of bangs, including frequency and loudness.
- Notes about where the sound is loudest and whether it correlates with the water heater or main entry.
- Whether neighbors or the utility reported pressure events.
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.
- Avoid removing safety valves, unplugging appliances, or bypassing pressure switches yourself. These are there to protect your home and personal safety.
- Don’t ignore repeated loud bangs — persistent pressure surges can loosen fittings over time.
When to Call a Professional
Call a licensed plumber if any of the following apply:
- The bangs continue when no fixtures or appliances are running.
- You notice visible pipe movement, leaks, or new dripping at joints after a banging event.
- Your pressure regulator, well pump, or pressure tank may be involved — these require diagnosis and safe handling by a pro.
If the pattern points to supply-side issues, a plumber can confirm safely and advise whether the PRV, check valves, water hammer arrestors, or municipal supply need attention.
Safety Notes
- Leave safety devices in place. Don’t tamper with pressure switches, safety relief valves, or gas controls on water heaters.
- If you suspect a major pressure spike or a failing pressure device, shut off the main water only if you know how to do it safely and have the plumber’s number ready. Otherwise, wait for the pro.
- Keep clear access to the water heater and main shutoff so a technician can inspect equipment quickly.
Common Homeowner Questions
- What if the banging only happens at night? — Night-only bangs often point to automatic equipment cycling (well pumps, irrigation) or municipal pressure changes; log times and check with neighbors.
- Can I fix a PRV myself? — Adjusting or replacing a PRV is not a DIY job for most homeowners; it requires pressure testing and safe handling, so call a plumber.
- Will pipe insulation stop the noise? — Insulation can muffle sound but won’t stop the underlying pressure surges; source diagnosis is the priority.
For more related articles, see the Random Banging With No Water Running hub.