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

The maximum number of lavatories that can be connected to a 2-1/2 inch horizontal waste line is determined by plumbing codes, which establish specific allowances based on pipe diameter and fixture unit calculations. In this case, a 2-1/2 inch waste line can accommodate a specific number of fixture units used by lavatories.

According to even widely accepted plumbing standards, a 2-1/2 inch waste line typically has the capacity for a maximum of 14 fixture units. Since each lavatory contributes a certain number of fixture units, this allows for the maximum connection of up to 14 lavatories to be effectively drained without overwhelming the system or risking clogging.

Ensuring the proper number of fixtures connected to a given waste line diameter is crucial for maintaining an efficient plumbing system. In practice, exceeding this number could lead to drainage issues, including slow draining or backups, which is why understanding these capacity limits is essential for successful plumbing design and installation.