F80 Water Supply and Fire Suppression 4 — Questions and Answers
Question 1: What is the minimum residual pressure required at the outlet of a fire hydrant during flow testing per NFPA 291?
- 10 psi
- 20 psi (Correct answer)
- 30 psi
- 50 psi
Correct answer: 20 psi
NFPA 291 requires a minimum residual pressure of 20 psi at the hydrant outlet during fire flow testing.
Question 2: A dry-pipe sprinkler system is most appropriate in locations where:
- Water pressure is insufficient
- Pipes may be exposed to freezing temperatures (Correct answer)
- Response time must be minimized
- The building has high ceilings
Correct answer: Pipes may be exposed to freezing temperatures
Dry-pipe systems use pressurized air or nitrogen to keep pipes dry, preventing water from freezing in unheated spaces.
Question 3: Which type of fire department connection (FDC) fitting is most commonly used in the United States?
- Storz coupling
- NST (National Standard Thread) (Correct answer)
- BSPT (British Standard Pipe Taper)
- Cam-lock fitting
Correct answer: NST (National Standard Thread)
NST (National Standard Thread), also called NH (National Hose), is the most widely used FDC fitting standard in the US.
Question 4: In a fire suppression water supply system, what does a 'dead-end main' refer to?
- A main that has been shut off permanently
- A water main fed from only one direction (Correct answer)
- A main with no active hydrants
- A main below the frost line
Correct answer: A water main fed from only one direction
A dead-end main is supplied from only one end, limiting flow capacity and creating water quality concerns.
Question 5: Which valve type is preferred for controlling water flow in fire protection systems because it provides a visual indication of its open or closed position?
- Globe valve
- Ball valve
- OS&Y (Outside Screw and Yoke) gate valve (Correct answer)
- Butterfly valve
Correct answer: OS&Y (Outside Screw and Yoke) gate valve
OS&Y gate valves expose the stem when open and retract it when closed, providing a clear visual indicator of valve position.
Question 6: What is the purpose of a pressure-reducing valve (PRV) in a high-rise building's standpipe system?
- Boost pressure on upper floors
- Prevent excessive pressure on lower floor hose connections (Correct answer)
- Regulate pump discharge pressure
- Control flow rate through the riser
Correct answer: Prevent excessive pressure on lower floor hose connections
PRVs limit outlet pressure at lower-floor hose connections where static pressure from elevation head could exceed safe hose handling limits.
Question 7: Under NFPA 13, what is the required design area for an Ordinary Hazard Group 1 wet-pipe sprinkler system?
- 1,000 sq ft
- 1,500 sq ft (Correct answer)
- 2,000 sq ft
- 3,000 sq ft
Correct answer: 1,500 sq ft
NFPA 13 requires a design area of 1,500 sq ft for Ordinary Hazard Group 1 wet-pipe sprinkler systems.
F80 Water Supply and Fire Suppression 4
What is the minimum residual pressure required at the outlet of a fire hydrant during flow testing per NFPA 291?