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Failing steam traps and valves can mean serious trouble for your machines and equipment. One of the most common ways for steam traps and valves to fail is an event known as water hammer. Water hammer is the informal name for hydraulic shock, a detrimental process that occurs in steam traps and valves used to help control the movement of fluids, such as liquids and steam.

During water hammer, these moving fluids experience a sudden and powerful change in momentum, either changing direction or completely stopping, causing a high-pressure shockwave that spreads through a piping system, wreaking havoc on subsequent systems. This shockwave produces a banging or knocking sound that can be heard immediately after the shutoff takes place.

This sudden change in direction or complete stop occurs when an open steam trap or valve is abruptly closed. When the valve is closed, the water no longer has an open route to take, and it either slams mercilessly into the valve or reverses direction and flows back into the pump. Because water cannot be compressed, when the water impacts the steam traps and valves, it results in a shockwave that travels throughout the piping system and down to the next elbow, carrying with it the potential to cause serious damage to the pipelines if there is significant enough pressure. Other causes of water hammer include pump failure and check valve slam, which can occur during pump shutdown.

The Effects

While it may not seem like much of a threat on the surface, as the water travels through the piping, it continues to build up momentum, and when this force is suddenly halted, it creates pressure spikes that can reach an excess of 10 times the operating pressure of the system. All of this force is colliding and impacting with the steam traps and valves, and the resulting shockwaves produced can have disastrous and damaging effects on the overall piping system. This can occur from either one singular event or accrue over the course of multiple incidents.

This is why it’s important to actively monitor the health of your systems, such as with a smart analog sensor, which can preemptively detect and prevent pump failure, a leading cause of water hammer. Not only should you actively monitor for signs of steam trap and pump failure, but it’s critical to take immediate action as soon as the first warning signs of water hammer begin to appear. Failing to recognize and act on the alarms can ultimately lead to flow system failure and extensive system damage.

Water hammer requires swift and immediate action to prevent damage; failing to take action can have serious repercussions, including:

Pump and flow system damage: Recurring water hammer and the resulting force that it generates can cause considerable damage to other parts of the entire system, including pumps, steam traps, and valves. This causes undue stress and eventual failure to the gasketed and expansion joints, and can negatively affect the stability of the pipe walls and welded joints.

Leaks: Over time, water hammer can damage and degrade the integrity of parts such as fittings and joints, leading to leaks. The leaks often start small, but gradually intensify over time. Even these small leaks can cause serious damage to surrounding equipment if left not fixed.

Ruptured Pipelines: Because of the intense pressure spikes, water hammer can rupture pipelines, leading to an exceedingly expensive repair. Ruptures not only cause local pipelines to fail but can also cause the failure of other equipment and the overall system. The resulting damage is often extensive and requires a large replacement operation to fix.

Risk of Accidents: The resulting ruptured pipelines caused by water hammer can pose a serious threat to the health and safety of your employees. Uncontrolled leaks increase the risk of slips, falls, and electrocution.

Unscheduled Downtime: Water hammer and its damaging effects can lead to costly repairs and equipment replacement. During these required repairs, the business can experience additional financial losses due to downtime and loss of production.


One of the primary contributing factors of water hammer is the choice in check valve type. Certain types of valves, including swing, tilting disc, and piston-style check valves rely on gravity and flow reversal to close the valves. When the valves close, the water slams into the valves and steam traps, creating a damaging pressure wave that spreads throughout the piping system.

One alternative is silent or spring-assisted check valves, which are fitted with an internal spring that closed the valve before flow reversal occurs, effectively reducing or eliminating the potential for water hammer.

Another alternative solution for water hammer is the use of air chambers. Air chambers are systems that have a segment of piping, usually a tee-fitting pipe, with an empty or air-filled chamber acting as a shock absorber, allowing the water room to expand as it suddenly changes direction. This significantly reduces the force of the shock that would otherwise be directed at the pipeline.

Investments can also be made into sensor technology, such as UE System’s UltraTrak 850S, which monitors the health of your equipment and indicates the early onset of failure symptoms that lead to pump failure, a leading cause of water hammer.

Several other effective measures for preventing water hammer include:

  • Flushing old systems
  • Reducing the operating pressure
  • Adding pressure reducers and regulators in the supply line
  • Investing in air chambers for piping systems
  • Installing silent check valves to reduce the pressure

Failing steam traps and valves can have serious consequences on your valuable machinery and equipment, but by making the proper adjustments and continually monitoring the (health) of your systems, you can prevent disaster before it has a chance to start.