Massachusetts Plumbers Journeyman Practice Exam

In a PVC-DWV system, how much expansion allowance is required per ten feet length of pipe?

1. A. 1/4 inch

2. B. 1/2 inch

3. C. 1 inch

4. D. 2 inches

The correct answer is: B. 1/2 inch

In a PVC-DWV (Polyvinyl Chloride - Drain, Waste, and Vent) system, it is important to account for thermal expansion as the temperature of the plumbing system can fluctuate. PVC materials expand and contract due to temperature changes, and proper allowances must be made to prevent stress on fittings and joints that could lead to leaks or failures. The correct expansion allowance for PVC in a DWV system is generally recognized as 1/2 inch for every ten feet of piping. This means that for every ten feet of continuous PVC pipe, you should allow for a 1/2 inch of expansion. This allowance ensures that there is enough space for the pipe to expand when it heats up, such as in warm water applications, without putting undue pressure on connections or restricting flow. The other options represent allowances that are either too small or too large for practical applications. A smaller allowance, like 1/4 inch, would not provide sufficient space for expansion, potentially leading to stress and damage in the system. A larger allowance, such as 1 inch or 2 inches, would be excessive and could result in wasting space and materials in the installation process. Therefore, recognizing the correct expansion requirement is essential for maintaining the integrity and functionality of a