Massachusetts Plumbers Journeyman Practice Exam

How is a fixture supposed to be trapped?

1. Double trapped

2. Triple trapped

3. Not trapped

4. Single trapped

The correct answer is: Double trapped

The correct approach for trapping a fixture is that it should be single trapped. A fixture is designed to have a single trap that prevents sewer gases from entering a building while allowing wastewater to flow through. This single trap creates a water seal that serves as a barrier between the drainage system and the interior space, ensuring sanitation and safety. Double trapping, while perhaps adding an additional measure of security, can lead to complications such as increased potential for clogs and maintenance issues. Triple trapping is even more problematic, as it can create excessive resistance in the drainage system, leading to inadequate flow and more frequent backups. Not trapping a fixture at all would allow harmful sewer gases to enter the living space, which poses significant health risks. Thus, a single trap is the optimal and standard practice for plumbing fixtures, striking a balance between effective drainage and the prevention of odors or gases infiltrating the home.