Journeyman Plumbers Exam Gas Piping Systems 4 — Questions and Answers
Question 1: What substance is added to natural gas to give it its distinctive odor?
- Propane
- Methane
- Mercaptan (ethyl mercaptan) (Correct answer)
- Carbon monoxide
Correct answer: Mercaptan (ethyl mercaptan)
Mercaptan (ethyl mercaptan) is the odorant added to natural gas by the utility to make odorless gas detectable by smell at very low concentrations.
Question 2: Which of the following is the correct pipe thread sealant to use on gas piping threaded joints?
- Teflon tape only
- Pipe dope approved for gas service (Correct answer)
- Standard plumber's putty
- Silicone caulk
Correct answer: Pipe dope approved for gas service
Only pipe thread compound (pipe dope) specifically listed and approved for gas service should be used on gas pipe threaded joints; standard Teflon tape alone is not sufficient.
Question 3: When a gas appliance is installed in a bedroom or bathroom, which special requirement applies?
- The appliance must be direct-vent or have a sealed combustion chamber (Correct answer)
- The gas meter must be indoors
- No gas appliances are permitted in bedrooms or bathrooms
- A CO detector must be installed within 1 foot of the appliance
Correct answer: The appliance must be direct-vent or have a sealed combustion chamber
Gas appliances in sleeping rooms and bathrooms must use direct-vent or sealed combustion systems to prevent combustion air from being drawn from the occupied space.
Question 4: What is the primary purpose of a pressure regulator on a gas system?
- To increase gas pressure to appliances
- To reduce and stabilize supply pressure to a safe, usable level (Correct answer)
- To shut off gas flow during a leak
- To measure gas consumption for billing
Correct answer: To reduce and stabilize supply pressure to a safe, usable level
A pressure regulator reduces the higher distribution pressure to the lower, stable pressure required by appliances and maintains that pressure under varying flow conditions.
Question 5: CSST (corrugated stainless steel tubing) installations require bonding because:
- It corrodes faster than black steel pipe
- Lightning or electrical surges can arc through it and cause failures (Correct answer)
- It cannot withstand operating pressure without grounding
- Building codes require all metal piping to be bonded
Correct answer: Lightning or electrical surges can arc through it and cause failures
CSST must be bonded because lightning-induced electrical surges can arc through the thin corrugated walls, potentially causing pinhole leaks and gas fires.
Question 6: What is the minimum clearance required between unprotected gas piping and an electrical panel?
- 6 inches (Correct answer)
- 12 inches
- 18 inches
- No clearance requirement exists
Correct answer: 6 inches
Gas piping must maintain a minimum clearance of 6 inches from electrical panels and service equipment to reduce the risk of arcing igniting a gas leak.
Question 7: Which document primarily governs gas piping installation standards for most US jurisdictions?
- NFPA 54 / International Fuel Gas Code (IFGC) (Correct answer)
- IPC (International Plumbing Code)
- NEC (National Electrical Code)
- ASME B31.1 Power Piping
Correct answer: NFPA 54 / International Fuel Gas Code (IFGC)
NFPA 54 (National Fuel Gas Code) and its companion IFGC are the primary standards adopted by most US jurisdictions for fuel gas piping installation.
Journeyman Plumbers Exam Gas Piping Systems 4
What substance is added to natural gas to give it its distinctive odor?