GPT Gas Pipe Installation & Repair 2 — Questions and Answers
Question 1: When making a threaded connection on a gas piping system, what must be applied to the male threads?
- Teflon tape only
- Pipe joint compound approved for gas service or yellow Teflon tape (Correct answer)
- Any plumber's putty
- Epoxy adhesive
Correct answer: Pipe joint compound approved for gas service or yellow Teflon tape
Only pipe joint compound or Teflon tape specifically listed for gas service (yellow) may be used on threaded gas connections.
Question 2: What is the minimum burial depth for a metallic gas service line installed under a public roadway?
- 12 inches
- 18 inches
- 24 inches
- 36 inches (Correct answer)
Correct answer: 36 inches
NFPA 54 and most jurisdictions require at least 36 inches of cover for gas lines under roads subject to vehicle traffic.
Question 3: Which material is NOT acceptable for use as an indoor gas piping system in a residential application?
- Schedule 40 black steel
- CSST (corrugated stainless steel tubing)
- Type L copper (where permitted)
- PVC plastic pipe (Correct answer)
Correct answer: PVC plastic pipe
PVC and other non-metallic plastics are not approved for interior gas piping due to fire and UV degradation risks.
Question 4: A drip leg (sediment trap) is required immediately upstream of which component?
- Every elbow fitting
- Each gas appliance (Correct answer)
- The gas meter
- Each union fitting
Correct answer: Each gas appliance
A drip leg is installed immediately upstream of each gas appliance to capture moisture and debris before they enter the appliance.
Question 5: What is the correct procedure when a threaded union is needed in a gas piping system?
- Install it in any orientation with no restrictions
- Use only dielectric unions
- Install it in an accessible location and ensure it is union-rated for gas (Correct answer)
- Replace it with a compression fitting instead
Correct answer: Install it in an accessible location and ensure it is union-rated for gas
Gas unions must be rated for gas service and located in accessible areas so they can be inspected and serviced.
Question 6: When installing CSST, bonding is required primarily to protect against:
- Pressure surges from the utility
- Lightning-induced electrical arcing that can perforate the tubing (Correct answer)
- Carbon monoxide buildup
- Condensation corrosion inside the tube
Correct answer: Lightning-induced electrical arcing that can perforate the tubing
CSST must be bonded because indirect lightning strikes can induce electrical current that arcs through and perforates the thin corrugated stainless steel wall.
Question 7: What is the purpose of a pressure regulator installed on a residential gas system?
- To increase supply pressure for high-BTU appliances
- To reduce and stabilize the gas pressure delivered to appliances (Correct answer)
- To shut off gas flow during an earthquake
- To measure total gas consumption
Correct answer: To reduce and stabilize the gas pressure delivered to appliances
A pressure regulator steps down the higher street pressure to the safe, steady pressure required by residential appliances (typically 7 in. w.c.).
GPT Gas Pipe Installation & Repair 2
When making a threaded connection on a gas piping system, what must be applied to the male threads?