Journeyman Plumber License Exam 1
Questions And Correct Answers (Verified
Answers) Plus Rationales 2025
Question 1
What is the minimum slope required for a horizontal drainage pipe to ensure
proper drainage?
A) 1/16 inch per foot
B) 1/4 inch per foot
C) 1/2 inch per foot
D) 1 inch per foot
Rationale:
The minimum slope for horizontal drainage pipes (like drain or waste lines) is
generally 1/4 inch per foot to allow gravity to carry waste effectively without
causing blockages.
Question 2
Which type of pipe is commonly used for water supply lines in residential
plumbing due to its corrosion resistance and ease of installation?
A) Cast Iron
,B) Galvanized Steel
C) Copper
D) PVC
Rationale:
Copper is preferred for water supply lines because it is durable, corrosion-
resistant, and easy to install. Galvanized steel is less common now due to
corrosion issues. PVC is mainly used for drain, waste, and vent systems.
Question 3
The purpose of a vent pipe in a plumbing system is to:
A) Supply water to fixtures
B) Increase water pressure
C) Allow air to enter the drainage system to prevent traps from being siphoned
D) Remove waste from the building
Rationale:
A vent pipe allows air into the drainage system so that the water seals in traps
are not siphoned out, preventing sewer gases from entering the building.
Question 4
What is the main function of a P-trap installed under sinks?
A) To increase water flow speed
B) To trap debris before it enters the drain
C) To prevent sewer gases from entering the building by maintaining a water
, seal
D) To filter the water
Rationale:
A P-trap maintains a water seal that blocks sewer gases from coming back into
the building while still allowing wastewater to flow.
Question 5
Which type of fitting is used to join two pipes of different diameters?
A) Elbow
B) Coupling
C) Reducer
D) Tee
Rationale:
A reducer is designed to connect pipes of different sizes to maintain flow and
system integrity.
Question 6
What is the primary cause of backflow in a plumbing system?
A) High water pressure
B) Negative pressure or siphoning in the supply line
C) Water hammer
D) Excessive slope in drain lines
Questions And Correct Answers (Verified
Answers) Plus Rationales 2025
Question 1
What is the minimum slope required for a horizontal drainage pipe to ensure
proper drainage?
A) 1/16 inch per foot
B) 1/4 inch per foot
C) 1/2 inch per foot
D) 1 inch per foot
Rationale:
The minimum slope for horizontal drainage pipes (like drain or waste lines) is
generally 1/4 inch per foot to allow gravity to carry waste effectively without
causing blockages.
Question 2
Which type of pipe is commonly used for water supply lines in residential
plumbing due to its corrosion resistance and ease of installation?
A) Cast Iron
,B) Galvanized Steel
C) Copper
D) PVC
Rationale:
Copper is preferred for water supply lines because it is durable, corrosion-
resistant, and easy to install. Galvanized steel is less common now due to
corrosion issues. PVC is mainly used for drain, waste, and vent systems.
Question 3
The purpose of a vent pipe in a plumbing system is to:
A) Supply water to fixtures
B) Increase water pressure
C) Allow air to enter the drainage system to prevent traps from being siphoned
D) Remove waste from the building
Rationale:
A vent pipe allows air into the drainage system so that the water seals in traps
are not siphoned out, preventing sewer gases from entering the building.
Question 4
What is the main function of a P-trap installed under sinks?
A) To increase water flow speed
B) To trap debris before it enters the drain
C) To prevent sewer gases from entering the building by maintaining a water
, seal
D) To filter the water
Rationale:
A P-trap maintains a water seal that blocks sewer gases from coming back into
the building while still allowing wastewater to flow.
Question 5
Which type of fitting is used to join two pipes of different diameters?
A) Elbow
B) Coupling
C) Reducer
D) Tee
Rationale:
A reducer is designed to connect pipes of different sizes to maintain flow and
system integrity.
Question 6
What is the primary cause of backflow in a plumbing system?
A) High water pressure
B) Negative pressure or siphoning in the supply line
C) Water hammer
D) Excessive slope in drain lines
