Quick Answer:
If you only hear a plumbing noise while an appliance runs, it usually comes from water moving, a valve opening or closing, or a small pump or softener cycle. Run the appliance that makes the sound, note exactly when it happens (fill, drain, shutoff), and try a few simple checks. If the source is behind walls, in an attic, or part of an integrated system, a plumber can safely isolate and fix it.
Why This Happens
- Valve action: Many appliances open or close valves quickly. That sudden change can make pipes vibrate or produce a clicking, banging, or high-pitched noise.
- Flow and pressure: Filling and draining create short bursts of flow and pressure swings that show up as rattles, humming, or water hammer.
- Pumps and softeners: Built-in pumps, backwash cycles or water softener regeneration run on a schedule and can be noisy to a homeowner who notices only during those cycles.
- Thermal and mechanical vibration: Heat, vibration from motors, or loose straps let lines move and strike framing when an appliance starts or stops.
- Appliance-specific cycles: Some appliances add steam or run at unusual times, which can make plumbing noises clear only during that cycle—examples include Pipes noisy during dryer steam cycle and Noises only during irrigation hours.
Step-by-Step What to Do
Step 1 — Reproduce the noise on purpose
- Run the appliance cycle that triggers the noise. If it’s a washer, start a wash; if it’s a dishwasher, run a normal cycle.
- Note when the sound occurs: during the fill, while draining, or right at shutoff. That timing is one of the best clues to the cause.
Step 2 — Listen carefully and compare
- Stand near the appliance and then move along the likely pipe runs. Compare with other appliance cycles to see if the noise is unique to this device or similar to others.
- If you have more than one appliance of the same type, run those cycles too to compare timing and tone.
Step 3 — Feel the pipes and look for vibration
- While the appliance is running, gently touch accessible supply lines or exposed drain pipes to feel for vibration. A vibrating line points to loose straps, contact with framing, or a valve that’s vibrating.
- Do not open fittings or remove covers. Just touch externally and listen.
Step 4 — Do simple isolation tests
- Turn off the appliance or its supply valve briefly to confirm the noise stops when the device is off. That proves the appliance cycle is the trigger.
- Make a short video or audio recording of the noise and note the cycle phase—this helps a plumber diagnose it faster.
Step 5 — Take small fixes if obvious
- If you find a visibly loose pipe strap or clamp in an accessible spot, tightening it can stop rattles. Only tighten external fasteners; don’t open valves or fittings.
- If the noise seems related to a pump or softener cycle you cannot access, stop and call a pro rather than trying to rewire or disable it.
What Not to Do
- Don’t disassemble appliances or bypass safety devices to chase sounds.
- If the noise is tied to built-in systems like softeners or pumps, have a plumber diagnose it properly rather than trying to modify those systems yourself.
- Avoid working on pressurized lines, opening electrical panels, or removing covers that affect safety equipment.
When to Call a Professional
- When the noise comes from inaccessible piping inside walls, ceilings, or under slabs—these require isolation and testing tools a plumber has.
- If you find repeated water hammer, loud banging, or pressure-related cycling that you cannot fix with straps or obvious adjustments.
- If you suspect a pump, solenoid valve, or water-treatment cycle is at fault. A plumber can safely isolate those components, test them, and replace parts or add damping devices.
- If the noise coincides with leaks, reduced flow, or damage to fixtures—stop using the appliance and call a pro.
Safety Notes
- Shut off power to the appliance before doing any inspection that requires removing panels or covers. If unsure, leave electrical work to a technician.
- Never work on pressurized plumbing. Turning off a local shutoff valve is fine for an isolation test, but do not open fittings under pressure.
- Do not bypass pressure-relief or other safety devices to silence a noise—those devices protect your home and should remain in place.
Common Homeowner Questions
- Is this dangerous? Usually not immediately dangerous, but persistent pressure-related noises or leaks can cause damage or lead to failures; get help if it keeps happening.
- Can I fix it myself? You can run the tests described and tighten accessible loose straps, but anything behind walls, involving pumps, or electrical parts should be handled by a professional.
- Will the noise damage the appliance or plumbing? If left unchecked, vibrations and repeated water hammer can loosen fittings and cause wear; have a plumber inspect persistent problems.
For more related articles, see the Noises Only When Appliances Run hub.