Free Journeyman Plumbers Gas Piping and Appliances Questions and Answers — Questions and Answers
Question 1: A plumber is installing a natural gas piping system for a new residential furnace. According to most fuel gas codes, which of the following is a mandatory requirement for the piping installation just before the final connection to the furnace?
- A flexible appliance connector must be used for the final 3 feet of the connection.
- The piping must be painted yellow for identification purposes throughout its entire length.
- A sediment trap must be installed downstream of the appliance shutoff valve and as close to the appliance inlet as practical. (Correct answer)
- The gas pipe must be electrically bonded to the cold water piping within 1 foot of the appliance.
Correct answer: A sediment trap must be installed downstream of the appliance shutoff valve and as close to the appliance inlet as practical.
Most fuel gas codes, such as the IFGC and NFPA 54, require a sediment trap (also known as a drip leg or dirt leg) to be installed downstream of the appliance's shutoff valve. This device is designed to collect any sediment, debris, or moisture that may be in the gas line, preventing it from entering and damaging the appliance's sensitive gas controls. The trap is typically constructed with a tee fitting, a nipple at least 3 inches long, and a cap on the bottom.
Question 2: When installing Corrugated Stainless Steel Tubing (CSST) for a gas line in a residence, what is the minimum size copper bonding conductor required to be connected from the gas piping system to the building's electrical service grounding electrode system?
- 10 AWG
- 8 AWG
- 12 AWG
- 6 AWG (Correct answer)
Correct answer: 6 AWG
According to the International Fuel Gas Code (IFGC) and CSST manufacturer instructions, the bonding conductor for a CSST gas piping system must be no smaller than a 6 AWG copper wire or its equivalent. This bonding is crucial to protect the thin-walled tubing from damage due to electrical events like lightning strikes or power surges, which could otherwise create a fire or explosion hazard.
Question 3: A plumber needs to pressure test a newly installed natural gas piping system in a single-family home. The proposed maximum working pressure is less than 0.5 psi (14 inches water column). According to the International Fuel Gas Code (IFGC), what is the minimum required test pressure?
- 1.5 psi for 5 minutes
- 10 psi for 30 minutes
- 3 psi for 10 minutes (Correct answer)
- 5 psi for 15 minutes
Correct answer: 3 psi for 10 minutes
For a gas system with a proposed maximum working pressure less than 0.5 psi, the IPC and IFGC generally require a test pressure of not less than 1.5 times the working pressure, but no less than 3 psi. The test must be maintained for a minimum of 10 minutes with no perceptible drop in pressure. This ensures the integrity of the pipes and joints before any appliance is connected and the system is put into service.
Question 4: Which of the following locations is explicitly prohibited for the installation of a gas shutoff valve according to most model fuel gas codes?
- In the same room as the appliance
- Within a furnace plenum or concealed location (Correct answer)
- Outdoors, adjacent to the gas meter
- In a utility closet with other mechanical equipment
Correct answer: Within a furnace plenum or concealed location
The International Fuel Gas Code (IFGC) specifically prohibits the installation of shutoff valves in concealed locations and within furnace plenums. This is to ensure the valve is always accessible for emergency shutoff and to prevent the possibility of a gas leak directly entering the conditioned air distribution system.
Question 5: A plumber is installing 1-inch Schedule 40 steel pipe for a horizontal natural gas run. According to common piping standards (ASME B31.1), what is the maximum recommended support spacing for this horizontal pipe?
- 4 feet
- 12 feet
- 8 feet (Correct answer)
- 6 feet
Correct answer: 8 feet
While specific local codes may vary, standard engineering practices such as those referenced in ASME B31.1 provide tables for maximum support spacing. For 1-inch nominal steel pipe, the suggested maximum span is typically around 8 feet for gas service to prevent sagging and stress on the joints. Some tables might show 9 feet, but 8 feet is a very common and safe standard.
Question 6: A natural gas vent for a Category I appliance terminates through a pitched roof. What is the minimum height the vent must extend above the point where it passes through the roof surface?
- 6 inches
- 24 inches
- 12 inches (Correct answer)
- 18 inches
Correct answer: 12 inches
According to typical fuel gas codes, a vent must terminate at least a certain height above the roof to ensure proper draft and prevent blockage from snow or debris. For vents passing through a roof, a common minimum height requirement is 12 inches (1 foot), though this can increase depending on the roof pitch and proximity to vertical surfaces. For example, some codes require termination at least 2 feet higher than any portion of the building within 10 feet.
