AL GS Gas System Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the primary purpose of a gas pressure regulator?
A. To increase gas pressure
B. To maintain constant gas flow
C. To reduce and control gas pressure
D. To filter impurities
Rationale: A gas pressure regulator reduces the pressure from the
supply line to a safe level for appliances, ensuring proper operation.
2. What is the typical test pressure for a residential natural gas system?
A. 1 psi
B. 2 psi
C. 5 psi
D. 10 psi
Rationale: Residential gas systems are commonly tested at 10 psi to
ensure leak-tightness without overstressing the piping.
3. Which of the following materials is commonly used for underground
gas piping?
A. Copper
B. PE (Polyethylene) pipe
C. PVC
D. Galvanized steel
Rationale: PE pipe is corrosion-resistant and flexible, making it ideal
for underground natural gas installations.
4. What color coding is standard for natural gas piping?
A. Blue
, B. Green
C. Red
D. Yellow
Rationale: Yellow is the standard color to identify natural gas lines
for safety and maintenance purposes.
5. A gas appliance requires 0.5 psi at the inlet. The supply line provides 5
psi. What device is needed?
A. Gas meter
B. Shutoff valve
C. Pressure regulator
D. Relief valve
Rationale: A pressure regulator lowers the high supply pressure to
the appliance’s required 0.5 psi.
6. What is the minimum clearance for a gas appliance from combustible
materials?
A. 0 inches
B. 2 inches
C. 6 inches
D. 12 inches
Rationale: Most codes require a minimum clearance of 6 inches for
safe operation and to prevent fire hazards.
7. What is the function of a gas shutoff valve?
A. To regulate pressure
B. To measure gas flow
C. To stop gas flow in emergencies or maintenance
D. To filter gas impurities
Rationale: Shutoff valves provide a means to safely stop gas flow
when necessary.
8. How often should a gas system be inspected according to standard
codes?
A. Every month
B. Annually
C. Every 5 years
D. Only when problems occur
Rationale: Annual inspections ensure the system operates safely and
meet regulatory requirements.
, 9. Which device prevents backflow in a gas system?
A. Pressure regulator
B. Relief valve
C. Check valve
D. Gas meter
Rationale: Check valves allow flow in one direction and prevent
reverse flow, protecting the system.
10. What is the maximum allowable leak rate for gas piping during a
pressure test?
A. 1%
B. 2%
C. 5%
D. No detectable leak
Rationale: During testing, any detectable leak is unacceptable;
systems must be completely leak-free.
11. Which type of gas meter is most common in residential
applications?
A. Turbine meter
B. Diaphragm meter
C. Rotary meter
D. Ultrasonic meter
Rationale: Diaphragm meters are accurate at low flow rates typical in
homes.
12. What is the first step before starting any gas piping installation?
A. Connect the appliance
B. Test the system
C. Shut off the gas supply
D. Install the meter
Rationale: Safety protocols require shutting off the supply to prevent
accidental gas release.
13. When connecting gas appliances, which type of joint is
preferred?
A. Soldered copper joint
B. Threaded galvanized steel
C. Threaded black iron or approved flexible connector
D. PVC glue joint
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the primary purpose of a gas pressure regulator?
A. To increase gas pressure
B. To maintain constant gas flow
C. To reduce and control gas pressure
D. To filter impurities
Rationale: A gas pressure regulator reduces the pressure from the
supply line to a safe level for appliances, ensuring proper operation.
2. What is the typical test pressure for a residential natural gas system?
A. 1 psi
B. 2 psi
C. 5 psi
D. 10 psi
Rationale: Residential gas systems are commonly tested at 10 psi to
ensure leak-tightness without overstressing the piping.
3. Which of the following materials is commonly used for underground
gas piping?
A. Copper
B. PE (Polyethylene) pipe
C. PVC
D. Galvanized steel
Rationale: PE pipe is corrosion-resistant and flexible, making it ideal
for underground natural gas installations.
4. What color coding is standard for natural gas piping?
A. Blue
, B. Green
C. Red
D. Yellow
Rationale: Yellow is the standard color to identify natural gas lines
for safety and maintenance purposes.
5. A gas appliance requires 0.5 psi at the inlet. The supply line provides 5
psi. What device is needed?
A. Gas meter
B. Shutoff valve
C. Pressure regulator
D. Relief valve
Rationale: A pressure regulator lowers the high supply pressure to
the appliance’s required 0.5 psi.
6. What is the minimum clearance for a gas appliance from combustible
materials?
A. 0 inches
B. 2 inches
C. 6 inches
D. 12 inches
Rationale: Most codes require a minimum clearance of 6 inches for
safe operation and to prevent fire hazards.
7. What is the function of a gas shutoff valve?
A. To regulate pressure
B. To measure gas flow
C. To stop gas flow in emergencies or maintenance
D. To filter gas impurities
Rationale: Shutoff valves provide a means to safely stop gas flow
when necessary.
8. How often should a gas system be inspected according to standard
codes?
A. Every month
B. Annually
C. Every 5 years
D. Only when problems occur
Rationale: Annual inspections ensure the system operates safely and
meet regulatory requirements.
, 9. Which device prevents backflow in a gas system?
A. Pressure regulator
B. Relief valve
C. Check valve
D. Gas meter
Rationale: Check valves allow flow in one direction and prevent
reverse flow, protecting the system.
10. What is the maximum allowable leak rate for gas piping during a
pressure test?
A. 1%
B. 2%
C. 5%
D. No detectable leak
Rationale: During testing, any detectable leak is unacceptable;
systems must be completely leak-free.
11. Which type of gas meter is most common in residential
applications?
A. Turbine meter
B. Diaphragm meter
C. Rotary meter
D. Ultrasonic meter
Rationale: Diaphragm meters are accurate at low flow rates typical in
homes.
12. What is the first step before starting any gas piping installation?
A. Connect the appliance
B. Test the system
C. Shut off the gas supply
D. Install the meter
Rationale: Safety protocols require shutting off the supply to prevent
accidental gas release.
13. When connecting gas appliances, which type of joint is
preferred?
A. Soldered copper joint
B. Threaded galvanized steel
C. Threaded black iron or approved flexible connector
D. PVC glue joint
