CPD Sanitary Drainage Systems 3 — Questions and Answers
Question 1: A stack serving more than 10 branch intervals must be provided with a:
- Relief vent at the base
- Yoke vent at every fifth interval (Correct answer)
- Pressure-reducing valve
- Separate building drain connection
Correct answer: Yoke vent at every fifth interval
The IPC requires yoke vents (relief vents) at every fifth interval when a drainage stack serves more than 10 branch intervals to relieve pressure fluctuations.
Question 2: Which material is generally NOT approved for underground sanitary drain piping inside a building per the IPC?
- Cast iron
- Schedule 40 PVC
- ABS plastic
- Threaded galvanized steel (Correct answer)
Correct answer: Threaded galvanized steel
Threaded galvanized steel is not approved for underground sanitary drainage because it corrodes rapidly when buried and exposed to wastewater.
Question 3: In sanitary drainage design, what is a 'branch interval'?
- The spacing between cleanouts on a horizontal branch
- A vertical measurement of at least 8 feet along a drainage stack (Correct answer)
- The horizontal distance between two fixture connections
- The distance from the stack to the first fitting
Correct answer: A vertical measurement of at least 8 feet along a drainage stack
A branch interval is a vertical measurement of not less than 8 feet within a stack, representing the space between horizontal branch connections.
Question 4: Which of the following scenarios requires an indirect waste connection rather than a direct drain connection?
- A floor drain in a mechanical room
- A commercial dishwasher in a restaurant kitchen (Correct answer)
- A laundry standpipe for a washing machine
- A floor sink receiving condensate
Correct answer: A commercial dishwasher in a restaurant kitchen
Commercial dishwashers must discharge through an indirect waste connection with an air gap to prevent contamination of the potable or sanitary system by backflow.
Question 5: When a sanitary drain must pass under a footing, the minimum clearance between the top of the pipe and the bottom of the footing is:
- No clearance required if pipe is in a sleeve (Correct answer)
- 2 inches
- 4 inches
- 6 inches
Correct answer: No clearance required if pipe is in a sleeve
When a pipe passes under a footing, IPC allows it if properly sleeved or protected such that the footing load is not transferred to the pipe.
Question 6: What is the maximum distance a trap arm may extend horizontally from the trap weir to the vent for a 2-inch drain?
- 2 feet
- 4 feet
- 6 feet (Correct answer)
- 8 feet
Correct answer: 6 feet
Per IPC Table 909.1, a 2-inch trap arm has a maximum developed length of 6 feet from the trap weir to the vent.
Question 7: Which venting method uses a fitting designed with an internal air-admittance mechanism to vent individual fixtures?
- Circuit venting
- Air admittance valve (AAV) (Correct answer)
- Island venting
- Common venting
Correct answer: Air admittance valve (AAV)
An air admittance valve (AAV) is a mechanical vent device that opens under negative pressure to admit air and closes to prevent sewer gas escape.
CPD Sanitary Drainage Systems 3
A stack serving more than 10 branch intervals must be provided with a: