CO Gas Piping Contractor Exam
Questions and Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf
1. Which component of a gas piping system is primarily used to shut
off the gas supply to an appliance?
A. Sediment trap
B. Pressure regulator
C. Shutoff valve
D. Union
Rationale: A shutoff valve is installed so the gas supply to an
appliance or section of piping can be isolated for servicing,
maintenance, or emergency conditions. A sediment trap collects
debris and condensate, a regulator controls pressure, and a union
allows piping to be disconnected.
2. What is the primary purpose of a sediment trap in a gas piping
system?
,A. Increase gas pressure
B. Collect sediment and condensate before it reaches the appliance
C. Prevent gas from flowing backward
D. Measure gas consumption
Rationale: A sediment trap is designed to capture dirt, scale, moisture,
and other contaminants that could otherwise enter an appliance gas
valve or burner assembly. This helps protect appliance components
and maintain reliable operation.
3. Which material is commonly approved for aboveground interior
natural-gas piping when installed in accordance with applicable
requirements?
A. PVC water pipe
B. CPVC
C. Steel pipe
D. ABS
Rationale: Steel pipe is commonly used for fuel-gas distribution
systems. PVC, CPVC, and ABS are generally associated with other
piping applications and cannot simply be substituted for approved
fuel-gas piping.
4. What is the main purpose of a gas pressure regulator?
,A. Remove sediment from gas
B. Reduce or control gas pressure to the required level
C. Increase pipe diameter
D. Detect carbon monoxide
Rationale: Gas pressure regulators control the pressure delivered to
appliances or downstream portions of a piping system. Proper
pressure is necessary for safe and correct appliance operation.
5. Before performing work on an existing gas piping system, what
should be done first?
A. Remove all appliance burners
B. Increase the gas pressure
C. Shut off and isolate the gas supply as required
D. Open all appliance valves
Rationale: Gas must be safely isolated before work begins. This
reduces the possibility of uncontrolled gas release, fire, explosion, or
other hazards during installation or repair.
6. What is the purpose of a gas piping pressure test?
A. Determine the color of the pipe
B. Measure appliance efficiency
, C. Verify the piping system is gas-tight
D. Determine water pressure
Rationale: Pressure testing is used to demonstrate that a newly
installed or modified gas piping system does not leak. The applicable
test pressure, duration, and procedures are established by the
governing code and authority having jurisdiction.
7. Which condition is most likely to cause an unsafe gas piping
installation?
A. Properly supported pipe
B. Correctly sized piping
C. Accessible shutoff valve
D. An untested piping system placed into service
Rationale: A gas piping system should be tested according to
applicable requirements before being placed into service. Failure to
test can allow leaks to remain undetected and create a serious fire or
explosion hazard.
8. What is the primary purpose of sizing gas piping correctly?
A. Make the pipe look uniform
B. Provide adequate gas flow at the required pressure
Questions and Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf
1. Which component of a gas piping system is primarily used to shut
off the gas supply to an appliance?
A. Sediment trap
B. Pressure regulator
C. Shutoff valve
D. Union
Rationale: A shutoff valve is installed so the gas supply to an
appliance or section of piping can be isolated for servicing,
maintenance, or emergency conditions. A sediment trap collects
debris and condensate, a regulator controls pressure, and a union
allows piping to be disconnected.
2. What is the primary purpose of a sediment trap in a gas piping
system?
,A. Increase gas pressure
B. Collect sediment and condensate before it reaches the appliance
C. Prevent gas from flowing backward
D. Measure gas consumption
Rationale: A sediment trap is designed to capture dirt, scale, moisture,
and other contaminants that could otherwise enter an appliance gas
valve or burner assembly. This helps protect appliance components
and maintain reliable operation.
3. Which material is commonly approved for aboveground interior
natural-gas piping when installed in accordance with applicable
requirements?
A. PVC water pipe
B. CPVC
C. Steel pipe
D. ABS
Rationale: Steel pipe is commonly used for fuel-gas distribution
systems. PVC, CPVC, and ABS are generally associated with other
piping applications and cannot simply be substituted for approved
fuel-gas piping.
4. What is the main purpose of a gas pressure regulator?
,A. Remove sediment from gas
B. Reduce or control gas pressure to the required level
C. Increase pipe diameter
D. Detect carbon monoxide
Rationale: Gas pressure regulators control the pressure delivered to
appliances or downstream portions of a piping system. Proper
pressure is necessary for safe and correct appliance operation.
5. Before performing work on an existing gas piping system, what
should be done first?
A. Remove all appliance burners
B. Increase the gas pressure
C. Shut off and isolate the gas supply as required
D. Open all appliance valves
Rationale: Gas must be safely isolated before work begins. This
reduces the possibility of uncontrolled gas release, fire, explosion, or
other hazards during installation or repair.
6. What is the purpose of a gas piping pressure test?
A. Determine the color of the pipe
B. Measure appliance efficiency
, C. Verify the piping system is gas-tight
D. Determine water pressure
Rationale: Pressure testing is used to demonstrate that a newly
installed or modified gas piping system does not leak. The applicable
test pressure, duration, and procedures are established by the
governing code and authority having jurisdiction.
7. Which condition is most likely to cause an unsafe gas piping
installation?
A. Properly supported pipe
B. Correctly sized piping
C. Accessible shutoff valve
D. An untested piping system placed into service
Rationale: A gas piping system should be tested according to
applicable requirements before being placed into service. Failure to
test can allow leaks to remain undetected and create a serious fire or
explosion hazard.
8. What is the primary purpose of sizing gas piping correctly?
A. Make the pipe look uniform
B. Provide adequate gas flow at the required pressure
