Journeyman Plumbers Exam Gas Piping and Venting 3 — Questions and Answers
Question 1: What test pressure is typically used to pressure-test a new gas piping system before it is placed into service?
- Line pressure (standard operating pressure)
- 1.5 times the operating pressure, minimum 3 psig (Correct answer)
- 50 psig regardless of operating pressure
- 10 inches W.C.
Correct answer: 1.5 times the operating pressure, minimum 3 psig
NFPA 54 requires new gas piping to be tested at a pressure of at least 1.5 times the operating pressure or a minimum of 3 psig, whichever is greater.
Question 2: A sediment trap (drip leg) in a gas line is installed to:
- Reduce gas pressure before the appliance
- Collect condensate and debris before they enter the appliance (Correct answer)
- Prevent backflow of gas
- Measure gas flow rate
Correct answer: Collect condensate and debris before they enter the appliance
A sediment trap collects moisture and pipe scale, preventing them from entering the gas valve or burner of the appliance.
Question 3: What is the minimum burial depth for metallic gas service piping installed underground outside a building?
- 6 inches
- 12 inches
- 18 inches (Correct answer)
- 24 inches
Correct answer: 18 inches
Metallic gas piping buried outside must have a minimum cover of 18 inches to protect it from damage.
Question 4: Combustion air for a gas-fired water heater in a confined space can be provided by:
- One opening at the top of the space only
- Two permanent openings — one near the top and one near the bottom of the enclosure (Correct answer)
- A single large opening on any wall
- No openings are needed if the burner is sealed
Correct answer: Two permanent openings — one near the top and one near the bottom of the enclosure
A confined space requires two openings — one within 12 inches of the ceiling and one within 12 inches of the floor — to allow adequate air circulation.
Question 5: Which of the following is a correct statement about CSST (corrugated stainless steel tubing)?
- CSST may be run through air ducts without restriction
- CSST must be bonded and grounded per manufacturer and code requirements (Correct answer)
- CSST does not require protection where exposed to physical damage
- CSST is interchangeable with flexible appliance connectors
Correct answer: CSST must be bonded and grounded per manufacturer and code requirements
CSST must be bonded to the electrical grounding system to reduce the risk of arc damage from lightning-induced surges.
Question 6: A gas furnace is classified as a Category I appliance. This means its vent operates at:
- Positive pressure and produces excessive condensate
- Non-positive pressure and flue gases above dew point (no condensation) (Correct answer)
- Positive pressure with no condensation
- Negative pressure with excessive condensation
Correct answer: Non-positive pressure and flue gases above dew point (no condensation)
Category I appliances operate at non-positive vent pressure and produce flue gases warm enough to avoid condensation in the vent.
Question 7: What is the purpose of a union fitting in a gas piping system?
- To allow thermal expansion of the pipe
- To permit disconnection of sections of pipe without cutting (Correct answer)
- To reduce pipe diameter at an appliance connection
- To regulate gas pressure
Correct answer: To permit disconnection of sections of pipe without cutting
A union allows a section of gas pipe to be disconnected for servicing or appliance removal without cutting or disassembling the entire line.
