Quick Answer:
If you hear rattling only when you run hot water, it’s often a loose or expanding hot-water pipe rubbing against framing, cabinets, or a ceiling. First try a few simple checks you can do from the room: run the fixture slowly then fully to see when vibration starts, press lightly on nearby wall or cabinet to feel movement, and listen from an adjacent room to localize the run. If the pipe is inaccessible or the noise is near wiring or finished ceilings, a plumber can locate and secure the run safely without damaging the wall.
Why This Happens
Hot water changes temperature and pressure in the pipes. Two common causes are:
- Thermal expansion: hot pipes expand and shift against wood, drywall, or metal straps, producing a rattle only when the water is hot.
- Loose supports or straps: clamps, hangers, or insulation that worked for cold lines can be loose or broken on the hot-water run, allowing vibration that’s quieter at other times.
Where the pipe runs matters. If the run is above a ceiling or inside a wall, the sound may carry to other rooms—check both the ceiling and nearby rooms for clues. For similar problems in other locations, see Rattling in ceiling pipes and Rattling from basement ceiling.
Step-by-Step What to Do
Step 1 — Reproduce the noise methodically
- Run the fixture slowly then fully to see when vibration starts. Note whether it begins as the water gets hotter, when you open the valve all the way, or only during short bursts.
- Try other hot-water fixtures in the house (shower, kitchen sink, laundry) to see if they make the same sound. If only one fixture triggers it, the problem likely sits near that supply line.
Step 2 — Localize the run
- Listen from adjacent rooms and hallways to find the direction the sound travels. Quiet the house (turn off fans) so you can hear better.
- Press lightly on nearby wall or cabinet to feel movement. Put your hand flat against the surface while someone runs the hot water—sometimes you’ll feel a vibration even if the sound is faint.
Step 3 — Check visible supports and fixtures
- Look under sinks, in basements, and in accessible attics for loose straps or pipe insulation that’s shifted.
- If you can access the run safely and easily, tighten a loose clamp or add a foam pad between the pipe and the framing. Don’t force access or remove finishes to reach a pipe.
Step 4 — If access is limited, call to confirm rather than pry
- If the pipe is behind a finished ceiling, inside a wall, or near electrical wiring, a plumber can locate the exact run with non-invasive tools and secure it from an access point or behind a small access panel.
- Describe to the plumber when the rattling starts (slow flow, full flow, only hot) and where you felt or heard it—this speeds diagnosis.
What Not to Do
- Don’t open walls or wedge random shims blindly. Cutting into finished surfaces can create bigger repairs and may miss the real problem.
- Don’t hammer, force, or bend pipes to stop noise—you can damage fittings or create leaks.
- If the rattle is near wiring or finished ceilings, let a plumber locate the pipe first rather than poking around near electrical components.
When to Call a Professional
Call a licensed plumber if any of the following apply:
- You cannot locate the source after the basic checks.
- The pipe run is inside a finished ceiling or wall and you don’t have safe access.
- The rattling is accompanied by banging, leaks, or a drop in water pressure.
- The noise persists after tightening visible supports or adding padding.
A plumber can use inspection cameras, vibration meters, or remove small access panels to secure the pipe run safely and prevent damage to finishes.
Safety Notes
- Turn off water only if you know where the shutoff is and are prepared to deal with minor drips; if unsure, call a plumber.
- Avoid working near electrical wiring or gas lines. If the pipe run is close to wiring or finished ceilings, stop and call a professional.
- Do not attempt major repairs or open structural panels without the right permits and knowledge; unintended damage can be costly.
Common Homeowner Questions
- Will this damage my wall? Not immediately—most rattles are from movement, not leaks. But repeated rubbing can wear finishes over time, so locate and fix the source.
- Can I fix it myself? If the run and loose strap are accessible and you’re comfortable tightening clamps or adding padding, yes; otherwise call a plumber.
- Is it urgent? If there are no leaks and only light rattling, it’s not an emergency—but arrange a repair soon to avoid wear or a future leak.
For more related articles, see the Rattling Pipes Inside Walls hub.