Journeyman Plumbers Exam Gas Piping and Venting 2 — Questions and Answers
Question 1: What is the minimum clearance required between a gas appliance vent connector and combustible materials?
- 1 inch
- 3 inches
- 6 inches (Correct answer)
- 9 inches
Correct answer: 6 inches
NFPA 54 requires a minimum 6-inch clearance between single-wall metal vent connectors and combustible materials.
Question 2: When sizing a gas piping system, what is the primary factor used to determine pipe diameter?
- Operating pressure only
- Length of pipe only
- BTU demand and pipe length combined (Correct answer)
- Number of appliances only
Correct answer: BTU demand and pipe length combined
Gas pipe sizing requires both the total BTU demand of all appliances and the total developed length of the longest run to be considered.
Question 3: Which type of gas valve is required to be installed immediately upstream of each gas appliance?
- Ball valve only
- Accessible manual shutoff valve (Correct answer)
- Check valve
- Pressure relief valve
Correct answer: Accessible manual shutoff valve
An accessible manual shutoff valve must be installed within 6 feet of each appliance to allow quick isolation in an emergency.
Question 4: A Type B gas vent must terminate at least how far above the roof surface when the roof slope is 6/12 or less?
- 1 foot
- 2 feet (Correct answer)
- 3 feet
- 5 feet
Correct answer: 2 feet
For roof slopes of 6/12 or less, Type B vents must extend at least 2 feet above the highest point where the vent passes through the roof.
Question 5: What is the maximum allowable pressure drop for a low-pressure residential gas distribution system serving appliances?
- 0.2 inch W.C.
- 0.5 inch W.C. (Correct answer)
- 1.0 inch W.C.
- 2.0 inch W.C.
Correct answer: 0.5 inch W.C.
Low-pressure residential systems must not lose more than 0.5 inch W.C. between the meter outlet and any appliance connection.
Question 6: Which material is NOT approved for use in gas piping inside a residential building?
- CSST (corrugated stainless steel tubing)
- Schedule 40 black steel pipe
- Copper tubing (where approved by the local authority)
- PVC plastic pipe (Correct answer)
Correct answer: PVC plastic pipe
PVC plastic pipe is not approved for interior gas piping because it is not rated for gas service in most jurisdictions.
Question 7: When a gas vent connector passes through a combustible interior wall, what must be installed?
- An approved thimble or listed wall pass-through (Correct answer)
- A sheet metal collar only
- Fire-rated caulk only
- Nothing additional is required
Correct answer: An approved thimble or listed wall pass-through
An approved thimble or listed wall pass-through fitting must be used to maintain required clearances when a vent connector penetrates a combustible wall.
Journeyman Plumbers Exam Gas Piping and Venting 2
What is the minimum clearance required between a gas appliance vent connector and combustible materials?