CO Gas Piping Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A| Instant Download Pdf
1. What is the maximum allowable working pressure for a typical
residential natural gas system?
A. 2 psi
B. 5 psi
C. 0.5 psi
D. 1.5 psi
Rationale: Residential natural gas systems are normally limited to 0.5
psi (14 inches water column) to ensure safe operation.
2. Which material is NOT permitted for underground natural gas piping?
A. Polyethylene (PE)
B. Steel
C. Copper
D. Cast iron
Rationale: Copper is generally prohibited underground due to
corrosion and reaction with soil.
3. When testing a new gas line, what is the minimum pressure for a soap
test to detect leaks?
A. 5 psi
B. 3 psi
C. 2 psi
D. 1/2 psi
Rationale: A low-pressure soap test at 1/2 psi is sufficient to detect
leaks in new piping.
4. Which regulator is used to reduce high-pressure gas from the main to a
lower pressure for appliances?
, A. Backflow regulator
B. Relief regulator
C. Pressure regulator
D. Volume regulator
Rationale: Pressure regulators reduce distribution pressure to a safe,
usable level for appliances.
5. What is the minimum burial depth for polyethylene gas piping in
Colorado?
A. 6 inches
B. 12 inches
C. 18 inches
D. 24 inches
Rationale: PE gas piping must be buried at least 24 inches below
grade to prevent damage and frost heave.
6. For steel gas piping, what type of joint is preferred for high-
pressure systems?
A. Slip-on joint
B. Threaded joint
C. Soldered joint
D. Welded joint
Rationale: Welded joints provide maximum strength and leak
resistance for high-pressure steel piping.
7. What is the purpose of a vent in a gas appliance system?
A. Provide air for combustion
B. Remove combustion products safely
C. Increase gas flow
D. Reduce pressure
Rationale: Vents ensure combustion gases are safely exhausted
outside to prevent carbon monoxide buildup.
8. What is the primary safety concern when working with natural
gas piping? A. Corrosion
B. Leakage leading to explosion
C. Water infiltration
D. Freezing
, Rationale: Gas leaks can cause fires or explosions; preventing leaks
is the main safety concern.
9. Which code governs natural gas piping installation in Colorado?
A. NFPA 70
B. UPC
C. NFPA 54 / ANSI Z223.1
D. IPC
Rationale: NFPA 54 (National Fuel Gas Code) regulates natural gas
piping installations.
10. What is the required clearance from a gas meter to a source of
ignition? A. 1 foot
B. 2 feet
C. 3 feet
D. 6 feet
Rationale: Gas meters must be installed at least 3 feet from ignition
sources for safety.
11. When is it acceptable to use flexible gas connectors?
A. Underground main lines
B. Appliance connections
C. Between meters
D. High-pressure mains
Rationale: Flexible connectors are only allowed for final appliance
connections.
12. Which type of gas is lighter than air and can accumulate near
ceilings?
A. Propane
B. Natural gas (methane)
C. Butane
D. Carbon monoxide
Rationale: Methane is lighter than air and can rise to ceilings or
attics, creating an explosion hazard.
13. What is the minimum thread engagement for a 1-inch steel gas
pipe? A. 3/4 inch
B. 1 inch
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A| Instant Download Pdf
1. What is the maximum allowable working pressure for a typical
residential natural gas system?
A. 2 psi
B. 5 psi
C. 0.5 psi
D. 1.5 psi
Rationale: Residential natural gas systems are normally limited to 0.5
psi (14 inches water column) to ensure safe operation.
2. Which material is NOT permitted for underground natural gas piping?
A. Polyethylene (PE)
B. Steel
C. Copper
D. Cast iron
Rationale: Copper is generally prohibited underground due to
corrosion and reaction with soil.
3. When testing a new gas line, what is the minimum pressure for a soap
test to detect leaks?
A. 5 psi
B. 3 psi
C. 2 psi
D. 1/2 psi
Rationale: A low-pressure soap test at 1/2 psi is sufficient to detect
leaks in new piping.
4. Which regulator is used to reduce high-pressure gas from the main to a
lower pressure for appliances?
, A. Backflow regulator
B. Relief regulator
C. Pressure regulator
D. Volume regulator
Rationale: Pressure regulators reduce distribution pressure to a safe,
usable level for appliances.
5. What is the minimum burial depth for polyethylene gas piping in
Colorado?
A. 6 inches
B. 12 inches
C. 18 inches
D. 24 inches
Rationale: PE gas piping must be buried at least 24 inches below
grade to prevent damage and frost heave.
6. For steel gas piping, what type of joint is preferred for high-
pressure systems?
A. Slip-on joint
B. Threaded joint
C. Soldered joint
D. Welded joint
Rationale: Welded joints provide maximum strength and leak
resistance for high-pressure steel piping.
7. What is the purpose of a vent in a gas appliance system?
A. Provide air for combustion
B. Remove combustion products safely
C. Increase gas flow
D. Reduce pressure
Rationale: Vents ensure combustion gases are safely exhausted
outside to prevent carbon monoxide buildup.
8. What is the primary safety concern when working with natural
gas piping? A. Corrosion
B. Leakage leading to explosion
C. Water infiltration
D. Freezing
, Rationale: Gas leaks can cause fires or explosions; preventing leaks
is the main safety concern.
9. Which code governs natural gas piping installation in Colorado?
A. NFPA 70
B. UPC
C. NFPA 54 / ANSI Z223.1
D. IPC
Rationale: NFPA 54 (National Fuel Gas Code) regulates natural gas
piping installations.
10. What is the required clearance from a gas meter to a source of
ignition? A. 1 foot
B. 2 feet
C. 3 feet
D. 6 feet
Rationale: Gas meters must be installed at least 3 feet from ignition
sources for safety.
11. When is it acceptable to use flexible gas connectors?
A. Underground main lines
B. Appliance connections
C. Between meters
D. High-pressure mains
Rationale: Flexible connectors are only allowed for final appliance
connections.
12. Which type of gas is lighter than air and can accumulate near
ceilings?
A. Propane
B. Natural gas (methane)
C. Butane
D. Carbon monoxide
Rationale: Methane is lighter than air and can rise to ceilings or
attics, creating an explosion hazard.
13. What is the minimum thread engagement for a 1-inch steel gas
pipe? A. 3/4 inch
B. 1 inch
