Master Plumber Exam Gas Piping Systems 2 — Questions and Answers
Question 1: What is the maximum allowable pressure drop for a low-pressure gas system serving residential appliances?
- 0.3 inch water column
- 0.5 inch water column (Correct answer)
- 1.0 inch water column
- 2.0 inches water column
Correct answer: 0.5 inch water column
NFPA 54 allows a maximum pressure drop of 0.5 inch water column for low-pressure residential gas systems.
Question 2: Which material is NOT approved for use as a gas supply line inside a residential building?
- CSST (corrugated stainless steel tubing)
- Black steel pipe
- Galvanized steel pipe (Correct answer)
- Copper tubing (Type K or L)
Correct answer: Galvanized steel pipe
Galvanized steel pipe is not approved for interior gas piping because zinc coating can flake off and clog gas orifices.
Question 3: A gas dryer requires a shutoff valve located within how many feet of the appliance?
- 3 feet
- 4 feet
- 6 feet (Correct answer)
- 8 feet
Correct answer: 6 feet
The International Fuel Gas Code requires an appliance shutoff valve within 6 feet of the gas appliance it serves.
Question 4: What type of joint compound (pipe dope) is acceptable for gas piping connections?
- Any petroleum-based pipe dope
- Only PTFE tape
- Only compounds listed and approved for gas use (Correct answer)
- Standard plumber's putty
Correct answer: Only compounds listed and approved for gas use
Only thread sealants specifically listed and approved for gas service should be used on gas piping joints.
Question 5: When sizing a gas lateral, which factor is NOT used in the calculation?
- Total BTU demand of connected appliances
- Length of pipe run
- Available gas pressure
- Color of the pipe material (Correct answer)
Correct answer: Color of the pipe material
Pipe sizing calculations are based on BTU demand, pipe length, and available pressure — pipe color has no bearing on capacity.
Question 6: CSST (corrugated stainless steel tubing) must be bonded to the electrical grounding system primarily to protect against:
- Corrosion from soil contact
- Lightning-induced arc damage (Correct answer)
- Pressure surges from the utility
- Carbon monoxide buildup
Correct answer: Lightning-induced arc damage
CSST bonding is required because lightning-induced electrical surges can arc through the thin corrugated walls and cause gas leaks.
Question 7: What is the minimum burial depth for underground gas service piping in areas subject to physical damage?
- 6 inches
- 12 inches
- 18 inches (Correct answer)
- 24 inches
Correct answer: 18 inches
NFPA 54 requires underground gas piping to be buried at least 18 inches deep in areas where physical damage could occur.
Master Plumber Exam Gas Piping Systems 2
What is the maximum allowable pressure drop for a low-pressure gas system serving residential appliances?