BOC BOC Plumbing and Water Systems 1 — Questions and Answers
Question 1: What is the primary purpose of a backflow preventer in a building's plumbing system?
- To increase water pressure
- To prevent contaminated water from flowing back into the potable water supply (Correct answer)
- To reduce water hammer
- To filter sediment from incoming water
Correct answer: To prevent contaminated water from flowing back into the potable water supply
Backflow preventers stop contaminated or non-potable water from reversing flow and entering the clean drinking water supply due to back-pressure or back-siphonage.
Question 2: Which type of water heater is typically most energy-efficient for commercial buildings with high and consistent hot water demand?
- Tank-type electric water heater
- Tankless point-of-use heater
- Condensing boiler-based indirect water heater (Correct answer)
- Heat pump water heater
Correct answer: Condensing boiler-based indirect water heater
Condensing boiler-based indirect systems achieve very high efficiency by capturing flue gas heat and are well-suited for large, consistent commercial hot water loads.
Question 3: What does a pressure-reducing valve (PRV) do in a building water system?
- Boosts incoming water pressure to upper floors
- Steps down high street main pressure to a safe working pressure inside the building (Correct answer)
- Prevents water hammer in supply lines
- Regulates flow rate to individual fixtures
Correct answer: Steps down high street main pressure to a safe working pressure inside the building
A PRV reduces and stabilizes high incoming municipal water pressure to a safe level, typically 60–80 psi, to protect fixtures and piping from damage.
Question 4: Which test is used to check a sanitary drain system for leaks before walls are closed during construction or renovation?
- Hydrostatic pressure test (Correct answer)
- Air pressure test
- Smoke test
- Ball test
Correct answer: Hydrostatic pressure test
A hydrostatic (water) pressure test fills the drain system with water to check for leaks by monitoring water level loss over time.
Question 5: In a building's domestic hot water system, what is the purpose of a recirculation loop?
- To increase water heater capacity
- To ensure hot water is quickly available at fixtures without long wait times (Correct answer)
- To reduce incoming cold water pressure
- To allow dual-temperature zones
Correct answer: To ensure hot water is quickly available at fixtures without long wait times
A recirculation loop continuously circulates hot water through the distribution piping so occupants get near-instant hot water at any fixture.
Question 6: What type of valve should be installed as the main water shut-off for a building to allow full flow with minimal pressure loss?
- Globe valve
- Gate valve or full-port ball valve (Correct answer)
- Check valve
- Butterfly valve
Correct answer: Gate valve or full-port ball valve
Gate valves and full-port ball valves are designed for fully open or fully closed service with minimal pressure drop, making them ideal as main isolation valves.
BOC BOC Plumbing and Water Systems 1
What is the primary purpose of a backflow preventer in a building's plumbing system?