Journeyman Plumbers Exam Gas Piping and Venting 5 — Questions and Answers
Question 1: A gas appliance vent connector should slope upward toward the vent at a minimum of:
- 1/8 inch per foot
- 1/4 inch per foot (Correct answer)
- 1/2 inch per foot
- 1 inch per foot
Correct answer: 1/4 inch per foot
Vent connectors must rise at least 1/4 inch per foot toward the vent to ensure proper draft and prevent condensate from collecting in low spots.
Question 2: Propane (LP gas) differs from natural gas in that it:
- Burns cooler and requires less combustion air
- Is heavier than air and tends to settle in low areas (Correct answer)
- Is distributed at lower pressure than natural gas
- Cannot be used with the same appliances as natural gas without modification
Correct answer: Is heavier than air and tends to settle in low areas
Propane has a specific gravity greater than 1.0, so it sinks and accumulates in basements, pits, and low spots — creating a greater explosion risk than natural gas.
Question 3: When multiple gas appliances share a common vent, the common vent must be sized to handle:
- Only the largest appliance connected to it
- The total combined BTU input of all connected appliances (Correct answer)
- The average BTU input of connected appliances
- The smallest appliance, with separate vents for others
Correct answer: The total combined BTU input of all connected appliances
A common vent must be sized for the total combined BTU input of all appliances that connect to it at any time.
Question 4: What is the maximum length of an unprotected flexible appliance connector used on a gas range?
- 2 feet
- 3 feet
- 6 feet (Correct answer)
- 12 feet
Correct answer: 6 feet
Flexible connectors must not exceed 6 feet and must be the listed connector type appropriate for the appliance.
Question 5: A gas piping system installed in a commercial kitchen must be tested at what minimum pressure after installation?
- Standard operating pressure
- 3 psig for at least 10 minutes (Correct answer)
- 10 psig for at least 30 minutes
- 50 psig for one hour
Correct answer: 3 psig for at least 10 minutes
Commercial gas piping systems are commonly required to hold a test pressure of at least 3 psig for a minimum of 10 minutes with no detectable pressure drop.
Question 6: Which fitting is prohibited in a concealed gas piping installation?
- Welded fittings
- Mechanical press fittings listed for gas
- Flexible appliance connectors run through walls or floors (Correct answer)
- Wrought iron fittings
Correct answer: Flexible appliance connectors run through walls or floors
Flexible appliance connectors must never be concealed in or run through walls, floors, or ceilings because they cannot be inspected or replaced easily.
Question 7: What is the function of a pressure regulator installed on a gas service?
- To measure the volume of gas consumed
- To reduce and maintain steady downstream gas pressure (Correct answer)
- To shut off gas flow automatically if pressure drops
- To filter sediment from the gas supply
Correct answer: To reduce and maintain steady downstream gas pressure
A pressure regulator reduces high-pressure gas from the supply main to the lower, steady pressure required by appliances.
