Maryland Master Plumber/Gas Fitter Examination
Questions and Correct Answers (Verified Answers)
Plus Rationale 2027 Q&A| Instant Download Pdf
1. What is the primary purpose of a plumbing vent system?
A. Increase water pressure
B. Provide additional water to fixtures
C. Protect trap seals and allow proper drainage-system airflow
D. Reduce the temperature of wastewater
Rationale: A properly designed vent system allows air to enter and leave
the drainage system so wastewater can flow without creating excessive
pressure or siphoning trap seals. Maintaining trap seals helps prevent
sewer gases from entering occupied spaces.
2. Which fitting is generally used to change the direction of a drainage
pipe by approximately 90 degrees while maintaining a smooth flow
path?
A. Sanitary tee
B. Long-sweep quarter bend
,C. Straight coupling
D. Cap
Rationale: Long-sweep fittings provide a gradual change in direction
that reduces turbulence and minimizes the likelihood of blockages.
Drainage systems generally require fittings designed specifically for
smooth directional changes.
3. What is the main function of a plumbing trap?
A. Increase fixture pressure
B. Remove sediment from potable water
C. Maintain a water seal that prevents sewer gases from entering a
building
D. Increase drainage velocity
Rationale: A trap retains a quantity of water after a fixture is used. This
water forms a seal between the fixture and the drainage system,
preventing sewer gases from traveling into the building.
4. Which condition is most likely to cause a trap to lose its water seal
because wastewater flowing through the drainage system creates
negative pressure?
A. Backpressure
B. Thermal expansion
,C. Siphonage
D. Corrosion
Rationale: Siphonage occurs when negative pressure develops in a
drainage system and draws water out of a fixture trap. Proper venting
helps equalize pressure and protect the trap seal.
5. What is the purpose of a cleanout in a drainage system?
A. Increase water pressure
B. Provide access for inspection and removal of obstructions
C. Prevent thermal expansion
D. Supply air to combustion appliances
Rationale: Cleanouts provide accessible openings through which
drainage piping can be inspected and mechanically cleared. They are
particularly important at locations where blockages are likely to occur.
6. Which device is designed to prevent contaminated water from
flowing backward into the potable water supply?
A. Pressure-reducing valve
B. Water hammer arrestor
C. Backflow preventer
D. Thermostatic mixing valve
, Rationale: Backflow preventers protect potable water from
contamination caused by backpressure or backsiphonage. The specific
device required depends on the degree and type of cross-connection
hazard.
7. What is backsiphonage?
A. Excessive pressure caused by thermal expansion
B. Backflow caused by negative pressure in the potable water supply
C. Drainage caused by excessive vent pressure
D. Leakage through a fixture trap
Rationale: Backsiphonage occurs when pressure in the potable water
system falls below atmospheric or downstream pressure, allowing
water or other substances to be drawn backward into the potable
supply.
8. Which material is commonly used for potable water distribution
because it is corrosion-resistant and lightweight?
A. Cast iron
B. Copper
C. Clay
D. Concrete
Questions and Correct Answers (Verified Answers)
Plus Rationale 2027 Q&A| Instant Download Pdf
1. What is the primary purpose of a plumbing vent system?
A. Increase water pressure
B. Provide additional water to fixtures
C. Protect trap seals and allow proper drainage-system airflow
D. Reduce the temperature of wastewater
Rationale: A properly designed vent system allows air to enter and leave
the drainage system so wastewater can flow without creating excessive
pressure or siphoning trap seals. Maintaining trap seals helps prevent
sewer gases from entering occupied spaces.
2. Which fitting is generally used to change the direction of a drainage
pipe by approximately 90 degrees while maintaining a smooth flow
path?
A. Sanitary tee
B. Long-sweep quarter bend
,C. Straight coupling
D. Cap
Rationale: Long-sweep fittings provide a gradual change in direction
that reduces turbulence and minimizes the likelihood of blockages.
Drainage systems generally require fittings designed specifically for
smooth directional changes.
3. What is the main function of a plumbing trap?
A. Increase fixture pressure
B. Remove sediment from potable water
C. Maintain a water seal that prevents sewer gases from entering a
building
D. Increase drainage velocity
Rationale: A trap retains a quantity of water after a fixture is used. This
water forms a seal between the fixture and the drainage system,
preventing sewer gases from traveling into the building.
4. Which condition is most likely to cause a trap to lose its water seal
because wastewater flowing through the drainage system creates
negative pressure?
A. Backpressure
B. Thermal expansion
,C. Siphonage
D. Corrosion
Rationale: Siphonage occurs when negative pressure develops in a
drainage system and draws water out of a fixture trap. Proper venting
helps equalize pressure and protect the trap seal.
5. What is the purpose of a cleanout in a drainage system?
A. Increase water pressure
B. Provide access for inspection and removal of obstructions
C. Prevent thermal expansion
D. Supply air to combustion appliances
Rationale: Cleanouts provide accessible openings through which
drainage piping can be inspected and mechanically cleared. They are
particularly important at locations where blockages are likely to occur.
6. Which device is designed to prevent contaminated water from
flowing backward into the potable water supply?
A. Pressure-reducing valve
B. Water hammer arrestor
C. Backflow preventer
D. Thermostatic mixing valve
, Rationale: Backflow preventers protect potable water from
contamination caused by backpressure or backsiphonage. The specific
device required depends on the degree and type of cross-connection
hazard.
7. What is backsiphonage?
A. Excessive pressure caused by thermal expansion
B. Backflow caused by negative pressure in the potable water supply
C. Drainage caused by excessive vent pressure
D. Leakage through a fixture trap
Rationale: Backsiphonage occurs when pressure in the potable water
system falls below atmospheric or downstream pressure, allowing
water or other substances to be drawn backward into the potable
supply.
8. Which material is commonly used for potable water distribution
because it is corrosion-resistant and lightweight?
A. Cast iron
B. Copper
C. Clay
D. Concrete
