IPC Storm Drainage Systems 1 — Questions and Answers
Question 1: Per the IPC, what minimum slope is required for horizontal storm drain piping that is 3 inches or smaller in diameter?
- 1/8 inch per foot
- 1/4 inch per foot (Correct answer)
- 1/2 inch per foot
- 1/16 inch per foot
Correct answer: 1/4 inch per foot
The IPC requires a minimum slope of 1/4 inch per foot for horizontal storm drain piping 3 inches or smaller in diameter to ensure adequate flow velocity.
Question 2: According to the IPC, what is a 'conductor' in storm drainage terminology?
- An exterior vertical pipe that conveys storm water from the roof to grade
- A horizontal pipe connecting multiple roof drains
- A pipe inside a building that conveys storm water from the roof drain to the building storm drain (Correct answer)
- A pipe that carries electrical current for water heating systems
Correct answer: A pipe inside a building that conveys storm water from the roof drain to the building storm drain
A conductor is the vertical pipe located inside a building that carries storm water downward from the roof drain to the building storm drain.
Question 3: The IPC requires that roof drain strainers have a total inlet area of not less than:
- The same area as the conductor pipe
- Twice the area of the conductor pipe
- Three times the area of the conductor pipe
- 1.5 times the area of the conductor pipe (Correct answer)
Correct answer: 1.5 times the area of the conductor pipe
IPC Section 1102.4 requires roof drain strainers to have a total inlet area not less than 1.5 times the cross-sectional area of the conductor to prevent flow restriction.
Question 4: Per the IPC, secondary (emergency) roof drainage systems are required when:
- The roof area exceeds 5,000 square feet
- Overflow from blocked primary drains could cause structural damage or flooding of occupied areas (Correct answer)
- All flat roofs regardless of size must have secondary drains
- The building is located in a high-rainfall zone
Correct answer: Overflow from blocked primary drains could cause structural damage or flooding of occupied areas
The IPC requires secondary roof drainage where overflow from blocked primary drains poses a risk of structural damage or flooding of occupied building spaces.
Question 5: Under the IPC, 'area drains' are receptors designed to collect storm water from:
- Sanitary fixture discharge
- Roof surfaces only
- Exterior paved areas, courts, and similar surfaces (Correct answer)
- HVAC condensate equipment
Correct answer: Exterior paved areas, courts, and similar surfaces
Area drains are installed to collect and remove storm water from exterior paved or landscaped surfaces such as parking lots, driveways, and courtyards.
Question 6: Per the IPC, the design rainfall intensity used for sizing storm drainage systems must be based on:
- A uniform national standard of 4 inches per hour
- Rainfall data specific to the geographical location of the project (Correct answer)
- The lowest recorded hourly rainfall rate in the region
- The average annual rainfall divided by 8,760 hours
Correct answer: Rainfall data specific to the geographical location of the project
The IPC requires storm drainage to be sized using rainfall intensity data specific to the project location, typically from the code appendix tables.
Question 7: What is a 'leader' in IPC storm drainage terminology?
- The main horizontal building storm drain pipe
- An interior vertical pipe carrying roof water to the building drain
- An exterior vertical pipe or element that conveys storm water from the roof to the storm drain or grade (Correct answer)
- The licensed plumber responsible for inspections
Correct answer: An exterior vertical pipe or element that conveys storm water from the roof to the storm drain or grade
A leader (commonly called a downspout) is an exterior vertical pipe that carries storm water from the roof down to the storm drain or to grade level.
IPC Storm Drainage Systems 1
Per the IPC, what minimum slope is required for horizontal storm drain piping that is 3 inches or smaller in diameter?