DWV system layout, trap and vent requirements, and slope rules tested on plumbing licensing exams.
35 cards · basic cards · AI-written, checked twice. Edit anything.
- What does DWV stand for in plumbing?
Show answer
Drain, Waste, Vent - the system that removes used water and waste from buildings- Name the three main components of a DWV system
Show answer
Drainage (pipes carrying waste), waste fixtures (sinks, toilets), and vent system (allows air circulation)- What is a trap in a plumbing system?
Show answer
A U-shaped bend in a pipe that holds water to create a seal, blocking sewer gases from entering the building- What is the most common trap type used in modern residential plumbing?
Show answer
P-trap (petcock trap) - resembles the letter P- Why is the S-trap prohibited in most modern plumbing codes?
Show answer
It can self-siphon, causing the trap seal to be lost and allowing sewer gases to enter- What is trap seal depth?
Show answer
The vertical distance of water standing in the trap bend, typically 2 to 4 inches- What minimum trap seal depth is required by most plumbing codes?
Show answer
2 inches- Why is trap seal depth critical?
Show answer
If too shallow, water evaporates and the seal is lost; if too deep, it may discharge improperly- What is the proper slope for horizontal drainage pipes?
Show answer
1/4 inch per foot of pipe run (1 in 48 or approximately 2 percent grade)- What is the maximum allowable slope for horizontal drainage pipes?
Show answer
1/2 inch per foot (never more, as it can cause solids to settle improperly)- What happens when a drainage pipe has insufficient slope?
Show answer
Wastewater flows too slowly, causing solids to accumulate and pipes to clog- What is a trap arm in plumbing?
Show answer
The horizontal section of pipe between the trap outlet and the vent connection- What is the maximum length of a trap arm before a vent is required?
Show answer
Generally 2 to 3 feet depending on pipe diameter and code, but varies by jurisdiction- What is the purpose of cleanouts in a DWV system?
Show answer
To provide access for clearing blockages and inspecting the drainage system- How far apart should cleanouts be spaced in horizontal runs?
Show answer
No more than 100 feet apart, or at every change of direction exceeding 45 degrees
FlashKeepers