Why Do My Pipes Make a Knocking Noise?

Hearing your pipes knock when turning on or off the water is a common plumbing issue that can stem from a variety of causes, most of which relate to pressure changes, loose components, or disruptions in water flow within your plumbing system. It can be a mere nuisance or a more serious plumbing problem. We see it in new homes and older homes across Berks County.

Thermal Expansion of Pipes

Knocking noises from pipes, especially when hot water is running, are often caused by thermal expansion and contraction of the pipes, which can cause them to rub against surrounding surfaces such as joists. When hot water flows through pipes the metal expands. The expansion causes the pipes to rub or vibrate against nearby joists, studs, or other pipes. While this isn’t an urgent or serious problem, the knocking sound can be bothersome.

Water Hammer

One of the most frequent reasons for knocking pipes is what’s known as water hammer. Water hammer occurs when a valve or faucet is suddenly shut off, causing the water that was moving through the pipes to come to a rapid stop. The momentum of the moving water creates a shockwave, which travels through the plumbing system and can cause a loud banging or knocking noise. While water hammer is more commonly associated with turning the water off, a similar effect can sometimes be heard when water is first turned on, particularly if air has become trapped in the pipes or if pressure builds too quickly.

High Water Pressure

If the pressure in your plumbing system is too high, it can cause pipes to vibrate or knock when water flow is initiated. This is especially noticeable in older homes with metal piping or when multiple faucets or appliances are in use at the same time. High water pressure not only leads to noise but can also wear out fixtures and appliances more quickly.

Loose Pipes

Loose pipes are another common culprit that can cause an annoying knocking or banging sound. When pipes aren’t properly secured to the framing of your home, the force of water moving through them can cause them to rattle or bang against walls, floors, or other pipes. This is often more noticeable when water is turned on suddenly and can be exacerbated by long stretches of unsupported pipe.

Trapped Air in the Pipes

In some cases, air trapped in the pipes can cause a knocking or banging noise. When you first turn on a faucet, the trapped air can be forced through the system, creating a knocking sound until the air is flushed out. This is more common after plumbing repairs or after water service has been interrupted.

Herbein Plumbing Can Address Your Home’s Noisy Pipes

Call us today to schedule a visit to your home. We will thoroughly check your plumbing system to determine the cause of the noisy pipes. Possible recommendations could be installing or repairing air chambers, securing loose pipes, adjusting water pressure with a regulator, or draining the system to remove trapped air. 

Left unresolved, knocking pipe issues can worsen over time, potentially leading to leaks or damage to your plumbing system. It’s best to investigate persistent pipe noises promptly to avoid more serious complications.