Maryland Journeyman Plumber/Gas
Fitter Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationale 2026 Q&A| Instant Download
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1. In a residential plumbing system, what is the primary purpose of a trap
installed beneath a plumbing fixture?
A. To increase water pressure
B. To prevent sewer gases from entering the building
C. To improve drainage velocity
D. To separate solid waste from liquid waste
B. To prevent sewer gases from entering the building
Rationale: Plumbing traps retain a water seal that blocks harmful and
unpleasant sewer gases from traveling back through the drainage system
into occupied spaces. This water seal is a critical sanitary component
required by plumbing codes.
2. Which type of pipe is most commonly approved for underground
residential water service installations?
, A. Schedule 40 PVC
B. Type M copper
C. PEX tubing
D. Ductile iron pipe
D. Ductile iron pipe
Rationale: Ductile iron pipe is widely used for underground water service
due to its durability, strength, and resistance to external loads and
pressure. Although other materials may be permitted in some applications,
ductile iron is a standard choice for municipal and underground service
systems.
3. What is the minimum slope generally required for a 3-inch horizontal
drainage pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
B. 1/4 inch per foot
Rationale: Plumbing codes generally require horizontal drainage piping 3
inches or smaller to slope at least 1/4 inch per foot to maintain proper flow
velocity and prevent waste accumulation or blockages.
4. Which gas is primarily associated with the danger of carbon monoxide
poisoning from improperly vented gas appliances?
A. Nitrogen
B. Oxygen
C. Carbon monoxide
D. Methane
C. Carbon monoxide
,Rationale: Carbon monoxide is a colorless, odorless, and highly toxic gas
produced by incomplete combustion. Improper venting of gas-fired
appliances can allow carbon monoxide to accumulate indoors, posing
serious health risks.
5. What is the purpose of a plumbing vent system?
A. To increase water pressure
B. To remove solids from drainage piping
C. To maintain atmospheric pressure within the drainage system
D. To heat the drainage piping
C. To maintain atmospheric pressure within the drainage system
Rationale: Vent systems allow air to enter and circulate within drainage
piping, preventing siphonage of trap seals and ensuring proper drainage
flow. Proper venting is essential for system efficiency and sanitation.
6. Which fitting is designed to allow access for cleaning and inspection of
drainage piping?
A. Tee
B. Cleanout
C. Wye
D. Coupling
B. Cleanout
Rationale: Cleanouts provide access points to drainage systems for
maintenance, inspection, and removal of obstructions. Plumbing codes
specify cleanout locations throughout drainage systems.
7. In gas piping systems, what is the purpose of a sediment trap?
A. To reduce gas pressure
B. To collect moisture and debris
C. To increase gas velocity
D. To cool the gas line
, B. To collect moisture and debris
Rationale: Sediment traps are installed to collect condensate, dirt, and
debris before gas enters appliances. This helps protect appliance controls
and burners from contamination and malfunction.
8. Which plumbing fixture requires an air gap to protect the potable
water supply?
A. Lavatory faucet
B. Kitchen sink drain
C. Dishwasher
D. Bathtub overflow
C. Dishwasher
Rationale: Dishwashers can create a cross-connection hazard if wastewater
backs into the potable supply. Air gaps prevent contaminated water from
siphoning into drinking water systems.
9. What is the primary purpose of a pressure-reducing valve in a
plumbing system?
A. To increase flow rate
B. To lower excessive incoming water pressure
C. To filter sediment
D. To prevent water hammer
B. To lower excessive incoming water pressure
Rationale: Pressure-reducing valves regulate excessively high water
pressure entering a building, protecting plumbing fixtures, piping, and
appliances from damage and excessive wear.
10. Which test is commonly used to detect leaks in a newly installed
gas piping system?
A. Flow test
Fitter Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationale 2026 Q&A| Instant Download
1. In a residential plumbing system, what is the primary purpose of a trap
installed beneath a plumbing fixture?
A. To increase water pressure
B. To prevent sewer gases from entering the building
C. To improve drainage velocity
D. To separate solid waste from liquid waste
B. To prevent sewer gases from entering the building
Rationale: Plumbing traps retain a water seal that blocks harmful and
unpleasant sewer gases from traveling back through the drainage system
into occupied spaces. This water seal is a critical sanitary component
required by plumbing codes.
2. Which type of pipe is most commonly approved for underground
residential water service installations?
, A. Schedule 40 PVC
B. Type M copper
C. PEX tubing
D. Ductile iron pipe
D. Ductile iron pipe
Rationale: Ductile iron pipe is widely used for underground water service
due to its durability, strength, and resistance to external loads and
pressure. Although other materials may be permitted in some applications,
ductile iron is a standard choice for municipal and underground service
systems.
3. What is the minimum slope generally required for a 3-inch horizontal
drainage pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
B. 1/4 inch per foot
Rationale: Plumbing codes generally require horizontal drainage piping 3
inches or smaller to slope at least 1/4 inch per foot to maintain proper flow
velocity and prevent waste accumulation or blockages.
4. Which gas is primarily associated with the danger of carbon monoxide
poisoning from improperly vented gas appliances?
A. Nitrogen
B. Oxygen
C. Carbon monoxide
D. Methane
C. Carbon monoxide
,Rationale: Carbon monoxide is a colorless, odorless, and highly toxic gas
produced by incomplete combustion. Improper venting of gas-fired
appliances can allow carbon monoxide to accumulate indoors, posing
serious health risks.
5. What is the purpose of a plumbing vent system?
A. To increase water pressure
B. To remove solids from drainage piping
C. To maintain atmospheric pressure within the drainage system
D. To heat the drainage piping
C. To maintain atmospheric pressure within the drainage system
Rationale: Vent systems allow air to enter and circulate within drainage
piping, preventing siphonage of trap seals and ensuring proper drainage
flow. Proper venting is essential for system efficiency and sanitation.
6. Which fitting is designed to allow access for cleaning and inspection of
drainage piping?
A. Tee
B. Cleanout
C. Wye
D. Coupling
B. Cleanout
Rationale: Cleanouts provide access points to drainage systems for
maintenance, inspection, and removal of obstructions. Plumbing codes
specify cleanout locations throughout drainage systems.
7. In gas piping systems, what is the purpose of a sediment trap?
A. To reduce gas pressure
B. To collect moisture and debris
C. To increase gas velocity
D. To cool the gas line
, B. To collect moisture and debris
Rationale: Sediment traps are installed to collect condensate, dirt, and
debris before gas enters appliances. This helps protect appliance controls
and burners from contamination and malfunction.
8. Which plumbing fixture requires an air gap to protect the potable
water supply?
A. Lavatory faucet
B. Kitchen sink drain
C. Dishwasher
D. Bathtub overflow
C. Dishwasher
Rationale: Dishwashers can create a cross-connection hazard if wastewater
backs into the potable supply. Air gaps prevent contaminated water from
siphoning into drinking water systems.
9. What is the primary purpose of a pressure-reducing valve in a
plumbing system?
A. To increase flow rate
B. To lower excessive incoming water pressure
C. To filter sediment
D. To prevent water hammer
B. To lower excessive incoming water pressure
Rationale: Pressure-reducing valves regulate excessively high water
pressure entering a building, protecting plumbing fixtures, piping, and
appliances from damage and excessive wear.
10. Which test is commonly used to detect leaks in a newly installed
gas piping system?
A. Flow test
