Unraveling the Mystery of What is a Water Hammer


Unraveling the Mystery of What is a Water Hammer

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When you suddenly shut off your faucet and hear a loud thump reverberating through your pipes, you're experiencing a water hammer. This common plumbing issue, also known as hydraulic shock, can create serious concerns for homeowners, disrupting the peaceful atmosphere of a house. While it might not seem threatening, a water hammer can cause tremendous damage if not addressed promptly and correctly.

Understanding Water Hammers

Water hammer is a phenomenon that occurs when a liquid, specifically water, in motion is forced to stop or change direction abruptly. This sudden halt sends a pressure wave through the water that propagates throughout the plumbing, causing pipes to shudder and vibrate. The result is a distinct banging or thumping noise, akin to a hammer striking, hence the term 'water hammer'.

Pivotal Factors of Water Hammer Formation


High velocity of water contributes to water hammer. If water is running swiftly through the pipes and is suddenly halted, it can create a significant pressure wave, leading to louder, stronger water hammer effects.

Pipe Size and Material

The size and material of pipes also impact the severity of water hammer. Smaller and rigid pipes are more susceptible to the phenomenon because they have less capacity to absorb the pressure wave.

Valve or Fixture Shut-Off Speed

Fast-closing valves lead to more abrupt water stoppages, resulting in intense water hammer effects. Toilets and washing machines often cause water hammer because they have automatic solenoid valves that shut off quickly.

Implications of Unaddressed Water Hammer

If left untreated, water hammer can lead to:

  • Damage to plumbing fixtures and appliances
  • Rupture or dislocation of pipes
  • Appearance of leaks
  • Flooding

Mitigating the Water Hammer Effect

Installing Water Hammer Arrestors

Water hammer arrestors are simple devices that comprise an air chamber and a piston or diaphragm that absorbs the water's force, preventing the water wave from banging against the pipe's end. Water hammer arrestors are often placed at the ends of plumbing runs, near fast-closing valves, to curb water hammer effects.

Setting Up Air Chambers

Air chambers work on a similar principle as water hammer arrestors, acting as shock absorbers. When the water flow is halted abruptly, the air in the chamber compresses, absorbing the shock wave and reducing water hammer.

Pressure Reducing Valves

Installing a pressure reducing valve helps regulate the water pressure within your pipes, preventing water hammer. These valves are especially beneficial for homes with significantly high water pressure.

Consulting Plumbing Experts

While you may take a few steps around your home to mitigate water hammer, it's crucial to have a licensed plumber inspect your system. They can identify the source of the problem and recommend the most effective solutions – whether it's a valve adjustment, an air chamber installation, or pipe replacement. Getting professional help is worth every penny, especially when considering the potential destructive effects of an unaddressed water hammer.

Understanding what water hammer is, why it occurs, and how to prevent it can save homeowners significant time, stress, and money in repairs. Remember, while occasional water hammer may seem harmless, repeated instances can degrade and damage your plumbing, leading to costly replacements. By being proactive in your plumbing maintenance and seeking professional help when needed, you can ensure that water hammer is a thing of the past.

Frequently Asked Questions About Water Hammer

What is the basic definition of a water hammer?

A water hammer, also known as hydraulic shock, is a pressure surge or wave resulting when a fluid, usually water, is forced to stop or change direction suddenly. This phenomenon often occurs in enclosed pipe systems.

What causes a water hammer in the plumbing system?

A water hammer typically results from the abrupt closure of a valve at the end of a pipeline system. The sudden stoppage of water flow can lead to a shock wave that travels back through the pipe, causing the water hammer effect.

What are the common signs of a water hammer?

The most common symptom of a water hammer is a loud banging or knocking sound in your pipes when a tap is turned off quickly. Severe water hammers can even result in damaged pipes, a significant drop in water pressure or cause the pipe to vibrate violently.

How does a water hammer affect pipes in the house?

A water hammer can stress your home's plumbing system. The sudden extra pressure can cause pipes to weaken or break, result in loose pipe mounts, and even lead to leaks. Over time, water hammers can lead to significant and expensive damage to the plumbing system.

Are there effective ways of preventing water hammer?

Yes, there are ways to prevent water hammer. The most effective method generally involves reducing the water velocity. This can be achieved by using water hammer arresters, pressure reducing valves or installing air chambers. Moreover, you can also prevent water hammer by ensuring that pipes are securely fastened.

What is a water hammer arrester and how does it work?

A water hammer arrester is a device used to absorb the shock wave produced by a sudden stoppage of water flow, hence preventing a water hammer. It contains a spring and an air cushion, which effectively absorb the force of the water hammer. The arrester can be attached to the water line in the vicinity of specific fixtures or valves.

Can normal wear and tear of pipes cause a water hammer?

Regular wear and tear of pipes do not typically cause a water hammer. However, it is essential to note that over time, the repeated occurrence of water hammers can lead to the wear of pipes which can result in leaks or even bursts.

Can fixing loose pipes solve a water hammer issue?

Fixing loose pipes can help to a certain extent, but it does not directly address the main cause of a water hammer, which is the sudden stoppage of water flow. However, securing loose pipes can mitigate the effects of a water hammer by reducing the vibrations and noises caused by the shock waves.

Can a significantly lowered water pressure lead to a water hammer?

No, a reduction in water pressure will not cause a water hammer. In fact, lower water pressure can actually help to prevent a water hammer because it slows down the rate at which water flows through your pipes, which decreases the likelihood of a sudden stoppage of flow.

Is it necessary to hire a professional to fix a water hammer issue?

While minor water hammer issues can potentially be fixed with do-it-yourself solutions, it is generally recommended to hire a professional for severe water hammer problems. Trained plumbers have the right tools and expertise to correctly diagnose and effectively resolve water hammer issues, thereby preventing possible damage to your plumbing system.


A water hammer is a pressure surge or wave that occurs when a fluid, normally a liquid but sometimes also a gas, is forced to stop or change direction suddenly; a momentum change. This phenomena can cause major problems in piping systems. Water hammers can be a common issue in homes and other buildings, causing noise, vibrations, and even damage if not properly managed.

Manifestations of what is a water hammer can include loud banging or thumping noises following the turning off of a tap or shutting of a valve, rapid vibrations that can be felt physically and even visible shaking in exposed piping systems. These may seem harmless at first, but if persistent, they could lead to serious damage to your pipes or fixtures, disturbing your peace and tranquility at home or in the workplace.

The key to dealing with water hammer lies in understanding its causes and taking appropriate preventative measures. This can range from installing air chambers or water hammer arresters, adjusting water pressure, securing loose pipes, among other remedies. So, if you hear that familiar thump in your pipes, remember it's not a ghost playing tricks, it's what is a water hammer. And it's high time to take action.

About West Coast Hydronics & Plumbing

Hey there! Welcome to West Coast Hydronics & Plumbing, your trusted Sacramento, CA-based full-service plumbing company. We've been proudly delivering top-notch plumbing services since our establishment, consistently aiding homeowners and businesses with all their plumbing, hydronic heating, and radiant heat needs. Over the years, we've earned a reputation for excellence for our swift, efficient, and affordable solutions. Our dedicated and experienced team understands the unique challenges of California's plumbing systems, it's why we're always ready to assist, diagnose and provide well-informed, cost-effective solutions to ensure the comfort and satisfaction of all our valued customers.