G33 Master Gas Pipe Fitter
Exam Practice Exam Questions
and Answers Plus Rationales
1. What is the primary purpose of a gas pressure regulator?
To reduce high gas pressure to a usable level
Regulators maintain a safe and consistent pressure for appliances
and piping systems.
2. Which type of pipe is commonly used for natural gas distribution
inside buildings?
Black steel pipe
Black steel is preferred because it is strong and can handle gas
pressures safely.
3. What is the minimum slope required for a horizontal gas piping
system to drain condensate?
¼ inch per foot
Proper slope prevents accumulation of condensate that can cause
corrosion or blockages.
4. Which fitting is used to change the direction of a gas line by 90
degrees?
Elbow
Elbows allow directional changes in piping while maintaining flow
integrity.
,5. What is the maximum allowable leak rate for a gas system during
testing?
0% (no detectable leaks)
Gas systems must be leak-free for safety; any detected leak
requires correction.
6. What is the most common method for testing gas piping for leaks?
Soap solution or gas leak detector
Applying soapy water or a detector reveals escaping gas bubbles
at joints.
7. What is the minimum distance required between a gas meter and
a window opening?
3 feet
This prevents gas from entering buildings through windows in case
of a leak.
8. What is the function of a gas shutoff valve?
To stop the flow of gas in an emergency or for maintenance
Shutoff valves allow isolation of the system for safety and service.
9. What material should not be used for gas piping in residential
applications?
PVC
PVC is not approved for natural gas or propane because it can
degrade or crack.
10. What is the required test pressure for a new residential gas
line using natural gas?
3 psi (pounds per square inch)
Testing at 3 psi ensures the system can handle normal operational
pressures safely.
,11. What is the typical maximum allowable operating pressure
for residential gas systems?
0.5 psi
Most residential systems operate at low pressure to reduce
hazards.
12. Which fitting is used to join two pipes of different sizes?
Reducer
Reducers adjust pipe diameters to maintain system flow and
connection integrity.
13. What is the purpose of a drip leg or sediment trap?
To catch debris and moisture before it enters the appliance
Drip legs protect burners and regulators from contaminants that
could cause malfunction.
14. Which code regulates the installation of gas piping in the
U.S.?
NFPA 54 / National Fuel Gas Code
NFPA 54 provides the standard requirements for safe gas
installations.
15. What is the minimum burial depth for underground gas
piping in residential areas?
12 inches
This protects underground pipes from damage during excavation
or other disturbances.
16. What is the main risk of improperly vented gas appliances?
Carbon monoxide poisoning
Incomplete combustion produces carbon monoxide, which is
odorless and deadly.
, 17. Which type of joint is commonly used for black steel gas
piping?
Threaded joint
Threaded joints provide a strong mechanical seal suitable for gas
piping.
18. What is the first step before performing any gas piping
installation?
Shut off the main gas supply
Shutting off the gas prevents accidental leaks and ensures safety
during work.
19. What is the typical allowable deviation in pipe length
alignment for threaded gas pipe?
½ inch per 10 feet
Small deviations are tolerated for threading and fitting alignment
without causing leaks.
20. What is the purpose of a pressure test gauge on a gas line?
To measure pressure and verify the system is leak-free
Gauges ensure the system holds pressure during testing, indicating
integrity.
21. What is the correct procedure if a gas leak is detected during
testing?
Shut off gas and repair the leak before retesting
Gas leaks must be fixed immediately to prevent fire or explosion
hazards.
22. What is the minimum clearance required between a gas
appliance and combustible materials?
6 inches
Exam Practice Exam Questions
and Answers Plus Rationales
1. What is the primary purpose of a gas pressure regulator?
To reduce high gas pressure to a usable level
Regulators maintain a safe and consistent pressure for appliances
and piping systems.
2. Which type of pipe is commonly used for natural gas distribution
inside buildings?
Black steel pipe
Black steel is preferred because it is strong and can handle gas
pressures safely.
3. What is the minimum slope required for a horizontal gas piping
system to drain condensate?
¼ inch per foot
Proper slope prevents accumulation of condensate that can cause
corrosion or blockages.
4. Which fitting is used to change the direction of a gas line by 90
degrees?
Elbow
Elbows allow directional changes in piping while maintaining flow
integrity.
,5. What is the maximum allowable leak rate for a gas system during
testing?
0% (no detectable leaks)
Gas systems must be leak-free for safety; any detected leak
requires correction.
6. What is the most common method for testing gas piping for leaks?
Soap solution or gas leak detector
Applying soapy water or a detector reveals escaping gas bubbles
at joints.
7. What is the minimum distance required between a gas meter and
a window opening?
3 feet
This prevents gas from entering buildings through windows in case
of a leak.
8. What is the function of a gas shutoff valve?
To stop the flow of gas in an emergency or for maintenance
Shutoff valves allow isolation of the system for safety and service.
9. What material should not be used for gas piping in residential
applications?
PVC
PVC is not approved for natural gas or propane because it can
degrade or crack.
10. What is the required test pressure for a new residential gas
line using natural gas?
3 psi (pounds per square inch)
Testing at 3 psi ensures the system can handle normal operational
pressures safely.
,11. What is the typical maximum allowable operating pressure
for residential gas systems?
0.5 psi
Most residential systems operate at low pressure to reduce
hazards.
12. Which fitting is used to join two pipes of different sizes?
Reducer
Reducers adjust pipe diameters to maintain system flow and
connection integrity.
13. What is the purpose of a drip leg or sediment trap?
To catch debris and moisture before it enters the appliance
Drip legs protect burners and regulators from contaminants that
could cause malfunction.
14. Which code regulates the installation of gas piping in the
U.S.?
NFPA 54 / National Fuel Gas Code
NFPA 54 provides the standard requirements for safe gas
installations.
15. What is the minimum burial depth for underground gas
piping in residential areas?
12 inches
This protects underground pipes from damage during excavation
or other disturbances.
16. What is the main risk of improperly vented gas appliances?
Carbon monoxide poisoning
Incomplete combustion produces carbon monoxide, which is
odorless and deadly.
, 17. Which type of joint is commonly used for black steel gas
piping?
Threaded joint
Threaded joints provide a strong mechanical seal suitable for gas
piping.
18. What is the first step before performing any gas piping
installation?
Shut off the main gas supply
Shutting off the gas prevents accidental leaks and ensures safety
during work.
19. What is the typical allowable deviation in pipe length
alignment for threaded gas pipe?
½ inch per 10 feet
Small deviations are tolerated for threading and fitting alignment
without causing leaks.
20. What is the purpose of a pressure test gauge on a gas line?
To measure pressure and verify the system is leak-free
Gauges ensure the system holds pressure during testing, indicating
integrity.
21. What is the correct procedure if a gas leak is detected during
testing?
Shut off gas and repair the leak before retesting
Gas leaks must be fixed immediately to prevent fire or explosion
hazards.
22. What is the minimum clearance required between a gas
appliance and combustible materials?
6 inches
