Water Hammer in Hydraulic Systems: What It Is and How to Prevent It

4 March 2025

Water hammer is one of the leading causes of failure in hydraulic systems, particularly in water distribution circuits. This sudden shock, usually caused by a rapid pressure change, can lead to serious consequences for plumbing systems and pipelines.

But what exactly is water hammer, and how can it be prevented? Find out in this article, developed with insights from our experts in industrial pumps and pumping stations.

What Is Water Hammer?

Water hammer is a pressure surge that occurs when the velocity of a fluid in a pipeline changes suddenly.

It typically happens when a valve or faucet is closed abruptly, or when a pump stops. At that moment, the moving fluid generates a shock wave that travels through the pipes, creating a pressure spike.

The consequences of water hammer can range from simple noises to severe damage to the piping system, including unwanted vibrations and structural failures.

What Causes Water Hammer?

The most common cause of water hammer in hydraulic systems is the sudden closing of a valve in the circuit. Even after closure, water continues moving at high speed inside the pipes. This abrupt change in velocity generates excessive pressure, creating a shockwave in the system.

However, other factors can also trigger water hammer:

Sudden pump shutdown: When the pump maintaining water flow stops abruptly, pressure changes rapidly, producing a shockwave similar to that caused by valve closure.
Temperature differences: In some cases, water hammer can be triggered by temperature variations between hot water and cold pipes, leading to condensation and pressure fluctuations.
Equipment failure: A faulty pump or improperly calibrated component can disrupt water flow and cause water hammer.

Beware of Aggravating Factors

These causes can be worsened by additional factors, such as mineral deposits, pipe corrosion, or even the presence of microorganisms in the system.

The Possible Consequences of Water Hammer

Water hammer can have devastating effects on industrial and multi-residential installations, especially when it occurs frequently or with high intensity.

Here are some possible consequences:

Pipe ruptures: The shockwave’s force can cause pipes to break, disrupting the system and requiring costly repairs.
Leaks: Hydraulic shocks can loosen fittings and seals, leading to leaks that compromise system integrity and cause material damage or resource loss.
Expansion tank damage: Sudden pressure fluctuations can weaken the membrane inside expansion tanks, which are essential for maintaining stable system pressure, jeopardizing both safety and performance.

Equipment deterioration: Repeated or excessive pressure variations can cause internal damage to critical equipment, such as electric pumps, boosters, compressors, and production machinery, increasing the risk of premature failure and operational downtime.

Consequences That Lead to Costs

The consequences outlined above can result in higher maintenance costs, unexpected production shutdowns, or even the failure of expensive equipment. This underscores the importance of identifying and preventing water hammer as soon as the first signs appear.

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How to Prevent Water Hammer

Several measures can be implemented to reduce the risk of water hammer and prevent damage to your installations.

Pressure Regulators

Installing a pressure regulator helps maintain consistent water pressure, reducing the risk of pressure surges in the system. This protects both pipes and plumbing fixtures from the effects of water hammer while ensuring optimal pressure levels.

Slow-Closing Valves

Slow-closing valves are equipped with mechanisms that gradually reduce water flow, preventing sudden stops that generate shockwaves. These valves not only prevent water hammer but can also help conserve water.

Water Hammer Arrestors

Another effective solution for protecting hydraulic systems from water hammer is installing water hammer arrestors. These devices absorb and dissipate the shockwave generated by sudden pressure changes.

There are two main types of water hammer arrestors:

Spring-loaded arrestors: These feature a piston that moves in response to pressure, absorbing shock and reducing impact on the system.
Membrane-style arrestors: These use a diaphragm to separate air and water, providing controlled pressure attenuation and preventing abrupt shockwave transmission.

Installing these devices significantly reduces the risk of damage to both equipment and piping, offering a reliable solution to extend the lifespan of your system and avoid costly production interruptions.

Check Valves

Check valves control fluid direction within the pipeline. When reverse pressure is detected, they close automatically to prevent backflow and mitigate water hammer. These valves are typically installed at critical points, such as water meters, drainage systems, and water heaters.

Air Release Valves

Air trapped inside pipes can increase the risk of water hammer. Installing air release valves helps remove trapped air, preventing vibrations and shocks associated with air pockets.

Water Hammer Testing: Assessing and Preventing Risks

When it comes to preventing water hammer, a water hammer test is an essential tool for understanding and controlling this phenomenon. This test simulates and analyzes the effects of sudden pressure changes in hydraulic systems, providing a solid basis for identifying the most effective solutions.

Key Objectives of Water Hammer Testing

Measure peak pressure levels: The test evaluates the pressure spikes generated by shockwaves, helping to identify critical system points.
Identify vulnerabilities: The test pinpoints components or pipeline sections most exposed to rupture or degradation.
Assess protective devices: The efficiency of water hammer arrestors, regulating valves, and other protective equipment is evaluated to confirm their effectiveness in mitigating hydraulic shocks.