Journeyman Plumbers Exam Gas Piping and Appliances 5 — Questions and Answers
Question 1: A gas piping system operating at pressures above ½ psig but not exceeding 2 psig is classified as:
- Low pressure
- Medium pressure (Correct answer)
- Intermediate pressure
- High pressure
Correct answer: Medium pressure
NFPA 54 classifies gas piping at pressures above ½ psig (14 inches WC) up to 2 psig as a medium-pressure system, requiring different materials and joining methods.
Question 2: What must be installed where gas piping passes through a foundation wall or concrete floor slab?
- A shutoff valve
- A protective sleeve or casing (Correct answer)
- A dielectric union
- An expansion loop
Correct answer: A protective sleeve or casing
Gas pipe must be sleeved where it passes through masonry or concrete to protect it from corrosion, soil movement, and to allow for expansion.
Question 3: Under the International Fuel Gas Code, underground gas piping must have a minimum cover of:
- 6 inches
- 12 inches
- 18 inches (Correct answer)
- 24 inches
Correct answer: 18 inches
IFGC requires a minimum of 12 inches of cover for underground gas piping in residential applications, though 18 inches is common for areas with vehicular traffic.
Question 4: A pilot light that repeatedly goes out on a gas appliance most likely indicates a problem with:
- The main gas valve
- The thermocouple or thermopile (Correct answer)
- The pressure regulator
- The vent cap
Correct answer: The thermocouple or thermopile
The thermocouple generates a small voltage when heated by the pilot flame; if it fails or is positioned incorrectly, it causes the safety valve to close, extinguishing the pilot.
Question 5: Which of the following actions is required after replacing a gas appliance regulator?
- Pressure test to 100 psig to verify regulator strength
- Verify outlet pressure with a manometer at the rated flow condition (Correct answer)
- Purge the line with nitrogen before restoring gas service
- Replace all downstream flexible connectors simultaneously
Correct answer: Verify outlet pressure with a manometer at the rated flow condition
After regulator replacement, outlet pressure must be verified under load conditions with a manometer to ensure it is set to the correct operating pressure (typically 3.5 inches WC for natural gas).
Question 6: Gas piping that is exposed and subject to physical damage, such as in a garage or mechanical room, must be protected by:
- Painting the pipe a bright color
- Installing a metal guard or bollard (Correct answer)
- Wrapping the pipe with rubber insulation
- Increasing the pipe wall thickness by one schedule
Correct answer: Installing a metal guard or bollard
Physical protection such as steel guards, bollards, or pipe sleeves is required where exposed gas piping is vulnerable to damage from vehicles or equipment.
Question 7: When a gas appliance is located in a confined space that is not connected to outside air, combustion air can be supplied by:
- Opening a nearby window during appliance operation
- Two permanent openings: one within 12 inches of the top and one within 12 inches of the floor (Correct answer)
- A single large opening sized at 1 square inch per 1,000 BTU/hr
- A mechanical exhaust fan running continuously
Correct answer: Two permanent openings: one within 12 inches of the top and one within 12 inches of the floor
NFPA 54 requires two permanent openings in a confined space — one high and one low — to allow natural convective circulation of combustion and dilution air.
