If you’ve ever shut off a faucet or washing machine and heard a loud bang, thump, or knocking sound inside your walls, you’ve likely experienced what plumbers call water hammer.
Although the noise can be alarming, the real concern is the pressure shock inside the plumbing system. Over time, repeated water hammer can damage pipes, fittings, and valves if it’s not addressed.
What Is Water Hammer?
Water hammer occurs when flowing water suddenly stops or changes direction.
Because water moving through pipes has momentum, it doesn’t stop instantly when a valve closes. Instead, the sudden stop creates a pressure wave that travels through the plumbing system, causing pipes to shake or bang against framing inside the walls.
This pressure shock produces the characteristic hammering sound homeowners hear.
Common Causes of Water Hammer
Fast-Closing Valves
Many modern appliances use quick-closing valves, including:
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Washing machines
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Dishwashers
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Ice makers
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Some modern faucets
These valves shut off water quickly, which can create the pressure surge responsible for water hammer.
Missing or Failed Air Chambers
Many plumbing systems include air chambers—vertical sections of pipe that contain air and act as shock absorbers for pressure changes.
Over time, these chambers can become filled with water, eliminating the cushion that helps absorb pressure spikes.
When this happens, pipes may begin banging when valves close.
Loose or Poorly Secured Pipes
Sometimes the issue isn’t the pressure wave itself but the movement of pipes inside walls or ceilings.
If pipes are not properly secured with mounting straps or supports, pressure changes can cause them to shift and strike surrounding structures, producing loud noises.
High Water Pressure
Excessively high water pressure increases stress on the plumbing system and makes pressure surges more intense.
Homes with high pressure may experience:
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Frequent pipe banging
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Noisy fixtures
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Increased wear on plumbing components
Pressure regulators can help keep water pressure within safe limits.
Why Water Hammer Shouldn’t Be Ignored
Occasional pipe noise might seem harmless, but repeated pressure shocks can lead to plumbing damage over time.
Possible consequences include:
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Loose pipe fittings
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Leaks in joints or valves
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Premature wear on appliances
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Pipe damage behind walls
Addressing the cause early helps prevent larger repairs later.
What Homeowners Can Check
There are a few basic steps homeowners can take when investigating pipe noise:
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Notice when the noise occurs (for example, when the washing machine stops filling)
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Check whether the sound comes from a specific fixture or appliance
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Observe whether the noise is getting louder or more frequent
Avoid attempting complex plumbing modifications without proper tools or experience.
Professional Solutions for Water Hammer
A plumber may recommend several solutions depending on the cause of the problem:
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Installing water hammer arrestors to absorb pressure shocks
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Re-securing loose pipes inside walls or basements
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Adjusting or installing a pressure-reducing valve
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Inspecting appliances that may be creating sudden shutoffs
These solutions help protect the plumbing system and eliminate the noise.
Don’t Ignore Noisy Pipes
Banging pipes are often a warning sign that pressure changes inside your plumbing system need attention. Addressing water hammer early helps protect pipes, appliances, and fixtures throughout the home.
Call us Today!
Doug the Plumber
Need Help With Noisy Plumbing?
If your pipes bang or knock when water shuts off, a professional inspection can identify the cause and prevent potential damage. Homeowners in the Comox Valley can contact Doug the Plumber to diagnose water hammer and restore quiet, stable plumbing.