306A Water Supply Systems 3 — Questions and Answers
Question 1: What is the minimum burial depth for a water service pipe in most Canadian jurisdictions?
- 0.6 m
- 1.0 m
- 1.2 m below the frost line
- At or below the local frost depth (Correct answer)
Correct answer: At or below the local frost depth
The water service pipe must be buried at or below the local frost depth to prevent freezing. In Canada, this depth varies significantly by region, from about 1.2 m in southern areas to over 2.4 m in northern regions.
Question 2: What type of copper tubing is required for above-ground water distribution within a building?
- Type K only
- Type L or Type M (Correct answer)
- Type DWV
- Any type of copper
Correct answer: Type L or Type M
Type L or Type M copper tubing is used for above-ground water distribution. Type L is more common due to its heavier wall thickness providing better durability, while Type M is acceptable for lower-pressure residential applications.
Question 3: What is the main advantage of PEX tubing over copper for water supply distribution?
- Higher pressure rating
- Resistance to freezing damage and flexibility for routing (Correct answer)
- Better heat transfer
- Lower coefficient of expansion
Correct answer: Resistance to freezing damage and flexibility for routing
PEX tubing is flexible, allowing it to bend around obstacles without fittings, and it can expand slightly without bursting if water freezes inside, making it more resistant to freeze damage than rigid copper.
Question 4: When connecting dissimilar metals in a water supply system (e.g., copper to steel), what must be used to prevent galvanic corrosion?
- Teflon tape
- A dielectric union or dielectric fitting (Correct answer)
- A standard coupling
- Solder joint
Correct answer: A dielectric union or dielectric fitting
A dielectric union separates the two dissimilar metals with an insulating material to prevent galvanic corrosion, which occurs when different metals are in direct contact in the presence of an electrolyte (water).
Question 5: What is the minimum hot water storage temperature required to prevent Legionella bacteria growth?
- 43°C
- 49°C
- 55°C
- 60°C (Correct answer)
Correct answer: 60°C
Hot water must be stored at a minimum of 60°C (140°F) to kill Legionella bacteria, which thrive between 20°C and 45°C. A mixing valve then tempers the water to a safe delivery temperature.
Question 6: What device is required on a water supply system to prevent municipal water from being contaminated by building plumbing?
- Water meter
- Backflow prevention device at the service entrance (Correct answer)
- Pressure-reducing valve
- Shut-off valve
Correct answer: Backflow prevention device at the service entrance
A backflow prevention device at the water service entrance prevents contaminated water from the building's plumbing system from flowing back into the municipal water supply, protecting public health.
306A Water Supply Systems 3
What is the minimum burial depth for a water service pipe in most Canadian jurisdictions?