Plumbing Terminology, Definitions, and Symbols
Why Vocabulary Is Tested
Codes are written in defined words. A question may turn on whether a pipe is a "fixture drain" or a "fixture branch," or whether a fitting is a "sanitary tee" or a "vent tee." Learn definitions as functional descriptions, not memorized labels: what the component does, where it sits in the system, and what it connects.
Core Terms to Master
Know the difference between a trap (the water seal), a trap arm (fixture drain between trap and vent), and a vent (protects the seal). Understand developed length, fixture unit, drainage fixture unit (dfu), supply fixture unit, building drain versus building sewer, stack versus branch, and the distinction between indirect waste and direct waste. Learn the terms for slope (fall), grade, and the meaning of "invert."
Symbols and Drawings
Candidates should read plan symbols: soil and waste lines, vent lines, water lines (cold, hot, hot-water return), gas, and storm drainage. Isometrics show vertical relationships that plans hide. Know that a circle with a cross often marks a floor drain, and that abbreviations (FD, CO, VTR, FCO) are code-adjacent shorthand. Trap questions often test which symbol indicates a cleanout versus a vent terminal.
Common Traps in Questions
Distractors swap "building drain" with "building sewer" (the sewer begins outside the foundation). Others confuse a "common vent" with a "wet vent," or treat a "circuit vent" as a stack vent. Watch for unit confusion: fixture units are not gallons per minute.
Worked Example
Rule of thumb: if a term describes where flow goes, ask "inside or outside the building?" and "above or below the flood level rim?" Those two questions resolve most definition items. For symbols, match the line style and label before choosing an answer.