Master Plumber Practice Exam

At what intervals shall cast-iron soil pipe stacks be supported?

1. Their base and each floor

2. Intervals of 10 feet

3. Intervals of 5 feet

4. Every other story

The correct answer is: Their base and each floor

Supporting cast-iron soil pipe stacks is critical to maintaining their structural integrity and ensuring proper function within a plumbing system. The correct answer outlines the requirement that such pipes must be supported at their base and at each floor level. This support is necessary because cast-iron pipes can be quite heavy and, without sufficient support, the weight can cause bending or sagging over time. Each floor provides a natural support point and ensures that the pipe remains vertical and aligned properly, which is essential for proper drainage and to prevent any blockages or failure in the system. Supporting the pipes only at certain intervals, such as every 5 or 10 feet, could lead to increased stress on the pipe at unsupported sections, making them vulnerable to damage. Similarly, relying on support every other story would not provide adequate reinforcement for the entire length of the pipe, especially considering the varying loads and stresses that can occur with changes in fluid dynamics and temperature. Thus, supporting at both the base and each floor guarantees that the structural and functional requirements of the plumbing system are met effectively.