PEX Pipe Ticking Noise Behind the Wall — Is It Normal?

I completely understand the concern — mysterious ticking coming from inside your walls sounds like the opening scene of a home repair horror story. But I can reassure you right away: this is one of the most benign plumbing noises there is.

Why PEX Ticks

PEX tubing has a coefficient of thermal expansion roughly 10 times greater than copper pipe. In practical terms, a 10-foot length of PEX carrying 120°F hot water will grow about 1 inch in length compared to its cold state. That same length of copper would grow only about 0.1 inch.

When hot water enters a section of PEX, the tubing physically gets longer and fatter. As it does, it rubs against anything it is touching — wood studs, joists, pipe clips, the edges of holes drilled through framing, other pipes, or insulation. Each little rub or slip produces a tick or click.

You hear it most when:

• The hot water first turns on. The biggest temperature change happens when the pipe goes from room temperature to hot water temperature.
• Right after the hot water is turned off. The pipe starts cooling and contracting, slipping back the other direction.
• In the first few minutes. Once the pipe reaches thermal equilibrium, the movement stops and so does the noise.

The ticking usually comes from the hot water lines. Cold water PEX rarely makes noise because the temperature difference between the pipe and the cold water is too small to cause significant expansion.

Is It Really Just Expansion?

Yes, in the vast majority of cases. But here are a few quick checks to be sure:

Does the noise only happen when you run hot water? If the ticking starts within seconds of turning on a hot faucet or shower and stops a few minutes after you turn it off, it is thermal expansion. Case closed.

Does the noise happen even when no water is running? If you hear ticking with no water flowing, it is not the PEX pipes. It could be your hardwood floor expanding or contracting, ductwork expanding from the furnace running, or settling noises in the house framing.

Is it a banging rather than ticking? A loud bang or thud is water hammer, which is a different issue caused by valves closing suddenly. Water hammer is a pressure shockwave, not thermal expansion.

Does it sound like it is in one specific spot? PEX expansion noise is usually heard along a section of wall rather than in one pinpoint location. A noise isolated to one spot could be a pipe rubbing against a sharp edge where it passes through a stud — still harmless, but easier to address.

Can You Reduce the Noise?

While the noise is harmless, it can be annoying, especially in quiet bedrooms at night. Here are some approaches:

Ensure the pipe has room to move. When PEX is run through holes in framing, the holes should be slightly oversized to allow the pipe to slide freely as it expands. If the pipe is wedged tightly through a hole or pinched by a clip, the expansion force builds up and then releases with a loud tick instead of a quiet slide.

Use proper PEX hangers and clips. Plastic suspension clips designed for PEX allow the pipe to slide while still supporting it. Metal hangers meant for copper can grip too tightly and create friction points. If you have access to the pipes (in an unfinished basement or utility area), check that the hangers are PEX-compatible.

Add insulation at contact points. Where PEX touches wood or other surfaces, a small piece of foam pipe insulation or even a wrap of felt between the pipe and the surface dramatically reduces noise. The insulation acts as a lubricant and sound dampener.

Lower the water heater temperature slightly. The less temperature change the pipe experiences, the less it expands. If your water heater is set at 140°F, reducing it to 120°F (which is the recommended setting for scald prevention anyway) reduces the thermal expansion proportionally. This will not eliminate the noise but may reduce it noticeably.

PEX vs. Copper — Why You Hear This Now

If your home was recently replumbed from copper to PEX (or was built new with PEX), the ticking is new to you because copper simply does not move enough to make noise. Many homeowners who repiped to PEX are surprised by this.

PEX has significant advantages over copper — it resists freezing, does not corrode, costs less, installs faster, and lasts decades. The thermal expansion noise is really its only drawback, and it is purely cosmetic.

If someone is telling you the ticking means your PEX was installed wrong, that is usually not accurate. Even perfectly installed PEX makes some noise. Poorly installed PEX (too tight through framing, wrong clips) makes more noise, but the noise itself does not indicate a leak, a failure, or a problem.

When to Actually Worry

The only PEX-related noise that warrants investigation is a hissing or spraying sound, which would indicate a leak at a fitting. PEX fittings (crimp, clamp, or expansion type) are the potential failure points, not the tubing itself. A hissing sound plus a water stain on the wall means you need a plumber.

If your water bill has been climbing alongside the wall noises, it is worth ruling out a leak — but in most cases, ticking PEX and a high water bill are unrelated coincidences.

Related: Water Hammer Noise When Dishwasher Fills · Hardwood Floor Squeaks Only in Winter · Water Bill Suddenly High With No Visible Leak