Massachusetts Plumbers Journeyman Practice Exam

If a trench is excavated below grade and the bottom does not form a bed for the pipe, what material should be used to provide a uniform bearing surface between joints?

1. Gravel

2. Concrete

3. Sand

4. Clay

The correct answer is: Sand

The correct choice is sand because it is an effective material for creating a uniform bearing surface in trench applications. Sand compacts well and provides a stable foundation that conforms to the shape of the pipe, ensuring that there are no pressure points that could cause damage or misalignment over time. Its granular nature allows for drainage, reducing the risk of water accumulation that can lead to soil instability. Conversely, while gravel is a common bedding material, it can create uneven surfaces and may not provide the same level of conformability as sand. Concrete would not be appropriate in this case since it is rigid and does not allow for settling or movement of the pipe, which can lead to cracking or breakage. Clay, on the other hand, tends to retain water and can expand or contract based on moisture levels, leading to instability and inadequate support for the pipes. Hence, sand is the preferred choice for establishing a secure and uniform bed for plumbing pipes.