Ontario Operator-in-Training (OIT) Practice Exam

What typically causes water hammer?

1. Slow-moving water in pipes

2. Excessive water pressure

3. Sudden stopping of moving fluid

4. Use of low-quality pipes

The correct answer is: Sudden stopping of moving fluid

Water hammer is a phenomenon that occurs when a fluid in motion is forced to stop or change direction suddenly. This rapid halt creates a pressure wave that travels through the fluid and can result in a banging or hammering noise within the pipes. The sudden change in momentum causes a spike in pressure, which leads to the characteristic sound and can potentially cause damage to the plumbing system if it occurs frequently. When considering the other options, slow-moving water in pipes does not contribute to water hammer, as the lack of movement leads to a more stable pressure situation. Excessive water pressure might cause other issues within a plumbing system, but it isn't the direct cause of water hammer itself. Using low-quality pipes may lead to other problems like leaks or reduced lifespan, but again, it is not a specific trigger for the water hammer effect. Therefore, the sudden stopping of moving fluid is the key factor in causing this phenomenon.