CSLB Class B General Contractor's License Practice Exam

What is the most common reason for noise in piping when a water fixture is turned on or off?

1. Hot water was used

2. Cold water was used

3. Pipe supports come into contact with metal piping

4. The walls are not up to code causing pipe failure

The correct answer is: Pipe supports come into contact with metal piping

When a water fixture is turned on or off, noise in the piping system is most commonly caused by pipe supports that come into contact with the metal piping. This contact can result from the movement of water within the pipes, which causes vibrations and subsequent rattling or banging noises. Metal pipes, when they expand or contract due to changes in temperature or water pressure, may shift slightly. If the pipes are not adequately insulated from the supports or if the supports are not properly spaced, this movement can create noise as the pipe rubs against or strikes the support. Such conditions can also lead to pipe damage over time due to wear and tear, and contribute to issues like water hammer, where shock waves from rapidly stopped or started water flow create loud banging sounds throughout the system. Utilizing sufficient and properly placed supports, as well as insulating the pipes, can help minimize these sounds and provide a quieter plumbing system. Understanding the relationship between pipe movement and support contact is crucial for maintaining both the effectiveness and longevity of the plumbing system.