Master Plumber Practice Exam 2026 - Free Plumber Practice Questions and Study Guide

The maximum number of sinks that one trap may serve is determined by plumbing codes and industry standards aimed at maintaining proper drainage and preventing blockages. Typically, one trap can effectively serve up to three single-compartment sinks. This is due to the way drainage systems are designed; having more than three sinks connected to a single trap can increase the risk of inadequate drainage and venting issues, which can lead to water backup and other plumbing problems.

For example, when multiple fixtures discharge wastewater into a single trap, the flow may be impeded if too many fixtures are connected, potentially causing slow drainage and unpleasant odors. The regulations are in place to ensure that plumbing systems function effectively and minimize maintenance issues for homeowners and plumbing professionals alike.

This standard serves to protect the integrity of the plumbing system while ensuring efficient operation, which is why the correct answer indicates that three single-compartment sinks can utilize one trap. The other options exceed the suggested limits for a single trap and could lead to plumbing complications.