Drainage, Waste, and Vent Systems Flashcards
7 cards from real Journeyman Plumbers Exam practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Drainage, Waste, and Vent Systems flashcards as text
Under the IPC, what is the maximum number of fixture units permitted on a 3-inch horizontal branch drain sloped at 1/4 inch per foot?
Answer: 20 DFUs
A 3-inch horizontal branch at 1/4-inch-per-foot slope can carry a maximum of 20 drainage fixture units per IPC Table 710.1(2).
Which of the following best describes back-pressure (positive pressure) in a drainage stack?
Answer: Pressure that builds below a slug of falling water and can push trap seals into the room
As a slug of water falls down a tall stack, it compresses air below it, creating positive pressure that can force trap seals out of lower-floor fixture traps.
A floor drain trap primer is used to:
Answer: Periodically supply water to a floor drain trap to prevent the seal from evaporating
Trap primers supply small amounts of water to infrequently used floor drain traps to replace water lost to evaporation and maintain the sewer gas seal.
What material is NOT permitted for use as a DWV pipe under the IPC in a concealed location?
Answer: Galvanized steel threaded pipe
Galvanized steel threaded pipe is not listed for DWV use under the IPC; approved materials include cast iron, ABS, PVC, and copper drainage tube.
A combination waste and vent system is typically used for:
Answer: Floor drains and sinks in slab-on-grade commercial kitchens where conventional venting is impractical
Combination waste and vent systems use oversized horizontal drain pipes as both the drain and vent, and are commonly applied to floor drains in slab construction where vertical venting is difficult.
When a drain pipe passes through a fire-rated assembly, what is required?
Answer: A listed fire stop or intumescent collar must be installed to maintain the fire rating
Any drain pipe penetrating a fire-rated floor, ceiling, or wall assembly must be protected with a listed firestop system or intumescent collar to restore the assembly's fire rating.
What test is commonly used to check a completed DWV system for leaks before covering it?
Answer: Air pressure test at 5 psi or water test filled to the highest point
DWV systems are tested with either an air test at 5 psi or a water test where the system is filled to the level of the highest stack opening, per IPC Section 312.