306A Water Supply Systems 2 — Questions and Answers
Question 1: What is the Water Supply Fixture Unit (WSFU) value for a standard residential water closet with a flush tank?
- 1.5
- 2.5 (Correct answer)
- 3.0
- 5.0
Correct answer: 2.5
A flush-tank water closet is rated at 2.5 WSFU, reflecting its moderate water demand during the fill cycle after flushing.
Question 2: When sizing water supply piping, what is the primary factor that determines friction loss?
- Water temperature
- Pipe material only
- Flow velocity and pipe length (Correct answer)
- Static pressure
Correct answer: Flow velocity and pipe length
Friction loss in water supply piping is primarily determined by the flow velocity (related to flow rate and pipe diameter) and the total developed length of the pipe run, including equivalent lengths for fittings.
Question 3: What is the maximum flow velocity recommended in water supply piping to minimize noise and erosion?
- 1.2 m/s (4 fps)
- 1.8 m/s (6 fps)
- 2.4 m/s (8 fps) (Correct answer)
- 3.0 m/s (10 fps)
Correct answer: 2.4 m/s (8 fps)
A maximum velocity of 2.4 m/s (8 fps) is recommended for water supply piping. Higher velocities cause excessive noise, erosion of pipe walls, and increased risk of water hammer.
Question 4: What material is commonly used for water service piping entering a building below grade in Canada?
- Galvanized steel
- Copper Type K (Correct answer)
- ABS
- PEX-AL-PEX
Correct answer: Copper Type K
Copper Type K is the heaviest wall thickness of copper tubing and is commonly used for underground water service because of its durability and resistance to soil corrosion.
Question 5: At what temperature must a thermostatic mixing valve (TMV) limit the output for public lavatory faucets to prevent scalding?
- 38°C
- 43°C
- 49°C (Correct answer)
- 55°C
Correct answer: 49°C
Thermostatic mixing valves for public lavatories must limit the water temperature to a maximum of 49°C (120°F) to prevent scalding injuries, especially for vulnerable populations.
Question 6: What is the purpose of a pressure-balancing valve in a shower installation?
- To increase water pressure to the showerhead
- To maintain consistent water temperature during pressure fluctuations (Correct answer)
- To reduce water consumption
- To prevent backflow into the supply
Correct answer: To maintain consistent water temperature during pressure fluctuations
A pressure-balancing valve senses changes in hot and cold supply pressures and adjusts flow to maintain a consistent mixed temperature, preventing sudden scalding or cold-water shock.
306A Water Supply Systems 2
What is the Water Supply Fixture Unit (WSFU) value for a standard residential water closet with a flush tank?