CSLB C-36 Plumbing ContractorRough-in PlumbingHard
A plumbing contractor is installing a new storm drainage system for a commercial building. The system includes a 6-inch diameter storm drain pipe that will be connected to a public storm sewer. What is the maximum allowable depth of water in this 6-inch storm drain pipe when flowing at design capacity, according to good engineering practice and common plumbing code principles?
- ATwo-thirds full (approximately 67% of pipe diameter)
- BCompletely full (100% of pipe diameter)
- CHalf full (50% of pipe diameter)
- DThree-quarters full (75% of pipe diameter)
Show answer & explanationAnswer & explanation
Correct answer: A. Two-thirds full (approximately 67% of pipe diameter)
Storm drains are typically designed to flow at a maximum of two-thirds full at design capacity. This allows for air circulation within the pipe and provides a margin for increased flow during peak rain events without surcharging the system.
Why the other options are wrong
- B. Completely full (100%) indicates a pressurized system or a surcharged gravity system, which is undesirable for storm drains as it eliminates air and surge capacity.
- C. Half full is a common design for sanitary sewers to maintain velocity, but storm drains can handle more.
- D. Three-quarters full is generally too high and risks surcharging the system and reducing hydraulic efficiency.
Storm Drain Design Flow Capacity
The maximum allowable water depth in a storm drain pipe under design conditions, ensuring efficient drainage and preventing surcharging.
- Allows for air circulation.
- Provides surge capacity.
- Prevents pressure buildup.
Memory trick: Storm Drains Safely Shed Surges.