Journeyman Plumbers Gas Piping and Venting Questions and Answers — Questions and Answers
Question 1: A plumber is using the longest length method to size a natural gas piping system. What is the first critical measurement required for this method?
- The total connected BTUH load of all appliances.
- The diameter of the gas meter outlet.
- The measured length of pipe from the point of delivery to the most remote gas outlet. (Correct answer)
- The gas pressure at the street main.
Correct answer: The measured length of pipe from the point of delivery to the most remote gas outlet.
According to the longest length method described in fuel gas codes, the initial step is to determine the measured distance from the gas meter (point of delivery) to the appliance furthest away in the piping system. This total length is then used in conjunction with the total appliance load to find the correct pipe size from the code's sizing tables.
Question 2: Which of the following gas appliances typically does NOT require the installation of a sediment trap according to most fuel gas codes?
- A gas-fired furnace.
- A residential gas water heater.
- A gas clothes dryer. (Correct answer)
- A commercial gas boiler.
Correct answer: A gas clothes dryer.
Most fuel gas codes provide exceptions for certain appliances from the requirement of a sediment trap. These often include illuminating appliances, ranges, and clothes dryers. The reasoning is that these appliances are typically attended during operation, and any issue with the flame would be quickly noticed. Furnaces and water heaters, which operate automatically, require a sediment trap to protect their controls.
Question 3: A high-efficiency condensing gas furnace is being installed. This appliance operates with a positive vent static pressure and produces acidic condensate. To which venting category does this appliance belong?
- Category I
- Category II
- Category III
- Category IV (Correct answer)
Correct answer: Category IV
Gas appliances are classified into four venting categories. Category IV appliances operate with a positive vent static pressure (fan-assisted) and have a low vent gas temperature that causes condensation. The vent must be airtight, watertight, and constructed of corrosion-resistant material like PVC or stainless steel, as specified by the manufacturer.
Question 4: When installing a flexible gas appliance connector for a residential gas range, what is the maximum permitted length according to most standards?
- 3 feet (0.9 m)
- 4 feet (1.2 m)
- 6 feet (1.8 m) (Correct answer)
- 10 feet (3 m)
Correct answer: 6 feet (1.8 m)
Standard codes, such as ANSI Z21.24, and fuel gas codes generally permit a maximum length of 6 feet (1.8 m) for flexible connectors serving appliances like ranges and dryers. This length allows the appliance to be moved for cleaning and servicing without disconnecting the gas line. It is prohibited to join two connectors together to extend the length.
Question 5: A journeyman plumber is installing a Corrugated Stainless Steel Tubing (CSST) gas line in a new residential construction. What is a critical safety requirement regarding the bonding of this piping system?
- The CSST itself must be used as the grounding electrode.
- A bonding clamp must be attached directly to the corrugated portion of the tubing.
- The system must be bonded to the electrical service grounding system with a #10 AWG copper wire.
- The system must be bonded to the electrical service grounding system with a conductor no smaller than a #6 AWG copper wire. (Correct answer)
Correct answer: The system must be bonded to the electrical service grounding system with a conductor no smaller than a #6 AWG copper wire.
To mitigate the risk of damage from an indirect lightning strike, both the National Fuel Gas Code and manufacturers' instructions require CSST to be bonded to the building's electrical service grounding system. This bonding jumper must be a copper wire no smaller than 6 AWG or its equivalent. The clamp should not be attached directly to the corrugated tubing itself but rather to a rigid pipe component or the CSST fitting.
Question 6: A plumber pressurizes a newly installed gas piping system for a leak test. For a typical residential system tested with air, what is the common minimum test pressure and duration required by code?
- 5 psi for 10 minutes
- 10 psi for 15 minutes (Correct answer)
- 50 psi for 30 minutes
- Working pressure for 24 hours
Correct answer: 10 psi for 15 minutes
Most plumbing and fuel gas codes require that a new gas piping system be subjected to a pressure test before being put into service. For a typical residential system, the test pressure must be at least 10 psi, and it must hold this pressure for a minimum of 15 minutes without any drop. The gauge used must be appropriate for this pressure range, typically with 1/10 psi increments.
Journeyman Plumbers Gas Piping and Venting Questions and Answers
A plumber is using the longest length method to size a natural gas piping system.
What is the first critical measurement required for this method?