CBI Plumbing & Mechanical Inspection 2 — Questions and Answers
Question 1: What is a backflow preventer and where is it required?
- A device that prevents contaminated water from flowing back into the potable water supply, required at cross-connections (Correct answer)
- A filter on the kitchen faucet
- A valve that increases water pressure
- A check valve on the sewer line
Correct answer: A device that prevents contaminated water from flowing back into the potable water supply, required at cross-connections
Backflow preventers protect the potable water supply from contamination by preventing reverse flow at cross-connections (irrigation systems, boiler feeds, chemical dispensers) where non-potable water could enter the drinking supply.
Question 2: What is the minimum hot water temperature at a residential water heater?
- 120°F is recommended by most codes and manufacturers to balance scald prevention and Legionella bacteria control (Correct answer)
- 100°F
- 140°F
- 180°F
Correct answer: 120°F is recommended by most codes and manufacturers to balance scald prevention and Legionella bacteria control
120°F is the standard recommended setting, balancing energy efficiency and scald risk with adequate temperature to limit Legionella bacteria growth (which thrives below 120°F).
Question 3: What is a cleanout in a plumbing system?
- An access fitting with a removable plug that allows clearing of blockages in drain and sewer lines (Correct answer)
- A cleaning port on the water heater
- A drain plug in a bathtub
- A faucet filter
Correct answer: An access fitting with a removable plug that allows clearing of blockages in drain and sewer lines
Cleanouts provide access points for snaking or jetting clogged drain lines. Codes require them at specific intervals, changes of direction, and at the building drain's connection to the sewer.
Question 4: What are the code requirements for combustion air in mechanical rooms?
- Adequate air supply must be provided for fuel-burning appliances to support complete combustion and safe operation (Correct answer)
- Combustion air is not code-regulated
- Only electric appliances need combustion air
- The HVAC system provides all needed air
Correct answer: Adequate air supply must be provided for fuel-burning appliances to support complete combustion and safe operation
Fuel-burning appliances (furnaces, water heaters, boilers) require adequate combustion air supply per mechanical code, provided through properly sized openings or ducts to prevent incomplete combustion and carbon monoxide production.
Question 5: What is a gas leak detection test and when is it required?
- A pressure test of gas piping using air or an approved gas to verify system integrity before placing it in service (Correct answer)
- A test performed only after a gas leak is reported
- An annual test of gas appliances
- A check of the gas meter reading
Correct answer: A pressure test of gas piping using air or an approved gas to verify system integrity before placing it in service
Gas line pressure testing verifies that all joints, connections, and piping are leak-free before the system is activated. The test involves pressurizing the system and monitoring for pressure drop over a specified period.
Question 6: What carbon monoxide detector requirements apply in residential construction?
- CO detectors are required outside each sleeping area and on every level of a home with fuel-burning appliances or attached garage (Correct answer)
- CO detectors are optional
- Only homes with gas stoves need CO detectors
- One CO detector per house is sufficient
Correct answer: CO detectors are required outside each sleeping area and on every level of a home with fuel-burning appliances or attached garage
Most jurisdictions require CO detectors outside each sleeping area and on every habitable level in homes with fuel-burning appliances (furnace, water heater, fireplace) or an attached garage, where CO infiltration can occur.
CBI Plumbing & Mechanical Inspection 2
What is a backflow preventer and where is it required?