Master Plumber Exam Gas Piping Systems 5 — Questions and Answers
Question 1: A gas-fired water heater installed in a garage must be elevated so the ignition source is at least how high above the floor?
- 6 inches
- 12 inches
- 18 inches (Correct answer)
- 24 inches
Correct answer: 18 inches
Appliances with open flames or ignition sources in garages must be elevated at least 18 inches above the floor to keep ignition above the level where heavier combustible vapors accumulate.
Question 2: When two or more gas appliances are served by a common vent, the vent must be sized based on:
- Only the largest appliance connected
- The smallest appliance connected
- The combined total BTU input of all connected appliances (Correct answer)
- The appliance farthest from the vent
Correct answer: The combined total BTU input of all connected appliances
Common vents must be sized for the total combined BTU input of all appliances connected to ensure adequate draft and safe flue gas removal.
Question 3: What is the purpose of an excess flow valve (EFV) on a gas service line?
- To boost low gas pressure at the meter
- To automatically shut off gas flow if the pipe is severed or flow exceeds a set threshold (Correct answer)
- To regulate pressure variations from the utility
- To prevent gas from flowing backward into the main
Correct answer: To automatically shut off gas flow if the pipe is severed or flow exceeds a set threshold
An excess flow valve automatically closes when gas flow exceeds a preset rate, such as when a service pipe is accidentally broken.
Question 4: Under IFGC, flexible gas connectors are prohibited from passing through:
- Floors or walls (Correct answer)
- Behind ranges in a kitchen
- Near a gas shutoff valve
- Adjacent to a drip leg
Correct answer: Floors or walls
Flexible gas connectors must not be concealed within or pass through floors, walls, ceilings, or partitions.
Question 5: A plumber discovers an existing uncoated steel gas pipe buried in soil. The correct action is to:
- Leave it if there are no visible leaks
- Wrap it with duct tape as a temporary fix
- Replace or coat it with approved corrosion protection (Correct answer)
- Increase the system pressure to offset corrosion effects
Correct answer: Replace or coat it with approved corrosion protection
Underground steel gas piping must be protected from corrosion with approved coatings or cathodic protection; uncoated pipe must be corrected.
Question 6: What is the maximum length of an outdoor LP gas appliance connector (flexible connector)?
- 3 feet
- 5 feet
- 6 feet (Correct answer)
- 10 feet
Correct answer: 6 feet
Outdoor LP appliance connectors, like those for gas grills, are also limited to a maximum of 6 feet in length.
Question 7: A plumber is installing a gas line and must cross an electrical panel location. The gas pipe must maintain a minimum clearance of how many inches from the panel?
- 3 inches
- 6 inches (Correct answer)
- 12 inches
- 24 inches
Correct answer: 6 inches
Gas piping must maintain a minimum of 6 inches clearance from electrical panels and equipment to reduce arc and ignition risk.
Master Plumber Exam Gas Piping Systems 5
A gas-fired water heater installed in a garage must be elevated so the ignition source is at least how high above the floor?