Understanding the Water Hammer Effect

The water hammer effect is a phenomenon often experienced in plumbing systems, particularly when a valve controlling the flow of water is shut off suddenly. This abrupt stoppage of water flow results in a significant increase in pressure, leading to a loud noise and potentially damaging the plumbing system. This can cause several issues, including damage to pipes and fixtures, leading to costly repairs and potential safety hazards.

Water Hammer Defined

Water hammer, also known as hydraulic shock, is primarily caused by the incompressibility of water. When a valve is shut off quickly, the still-moving water has nowhere to go, causing a substantial pressure surge. This pressure surge then travels through the pipe, manifesting as a sharp, loud noise and often leading to physical damage to the system.

Can Air Cause Water Hammer?

Oddly enough, the answer is no, at least not in the same way as water does. Air, being less dense and highly compressible, does not exhibit the same way of 'hammering' when valves are closed. Due to its compressibility, any sudden change in pressure caused by valve closure will dissipate quickly without creating the same kind of pressure surge.

Examples and Solutions

One real-life example of the water hammer effect occurred with a LG front-load clothes washer. When it starts filling, it initially requires a method to measure the water amount in the drum, leading to multiple bursts of water with the valve being shut off abruptly. This repeated action caused the water-supply pipe connectors to fail, necessitating replacement with brass fittings.

To mitigate this issue, a hammer tank was installed in the system, aiming to reduce the pressure surge. However, this did not provide a significant improvement. A more effective solution was to reduce the faucet pressure that feeds the hose to the washer, lowering the pressure from 90 psi to about 50 psi. This reduced the frequency of the water hammer but did not completely eliminate it.

Another interesting point is to imagine a 1.5L plastic bottle filled with water and dropped onto an orange from a height of 1 meter. The orange would be severely squashed, illustrating the impact of the water's momentum. If the bottle is empty and dropped, the orange will only show minor bruising, demonstrating how the absence of water (and thus the lack of a significant mass) greatly reduces the impact.

In industrial settings, water hammer can also occur, especially when high-pressure water systems are involved. However, the effects are often mitigated by the system design, which includes proper pipe sizing and support, as well as the use of dampeners and other protective measures.

Conclusion

Water hammer is a significant issue in plumbing and industrial systems, caused by the abrupt stoppage of water flow. While air in pipes does not cause the same 'hammering' effect due to its compressibility, the principles and mechanisms behind both phenomena are quite different. Understanding these differences is crucial for both homeowners and professionals to effectively manage and prevent these issues.