Journeyman Plumber Licensing Exam
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A |
Instant Download Pdf
1. What is the minimum water pressure required at a plumbing
fixture?
30 psi
This ensures proper fixture operation and prevents backflow
issues.
2. Which pipe material is most commonly used for residential water
supply lines?
Copper
Copper is durable, corrosion-resistant, and approved for potable
water.
3. What is the maximum distance a trap can be from a vent?
5 feet
This prevents siphoning and ensures proper drainage.
4. What is the purpose of a P-trap?
To prevent sewer gases from entering a building
The water in the trap forms a seal that blocks gases.
5. Which type of valve is best for emergency shut-off of water to a
fixture?
, Ball valve
Ball valves are quick to operate and provide a full shut-off.
6. What is the required slope for horizontal drainage pipes?
1/4 inch per foot
Proper slope ensures gravity drainage and prevents clogs.
7. Which code regulates plumbing installation standards in the U.S.?
Uniform Plumbing Code (UPC)
The UPC provides consistent safety and performance
requirements.
8. What is the standard thread type for most residential plumbing
fittings?
NPT (National Pipe Thread)
NPT threads provide a tight seal for metal pipe connections.
9. What is the typical size of a water service line to a single-family
home?
3/4 inch
This is sufficient to meet most residential water demand.
10. What type of water heater requires a vent to the outside?
Gas water heater
Gas water heaters produce combustion gases that must be safely
vented.
11. Which type of pipe is commonly used for gas distribution in
residential buildings?
Black steel
Black steel is durable and compatible with natural gas and
propane.
, 12. What is the minimum height for a plumbing vent above the
roof?
6 inches
This prevents backpressure and allows proper venting of sewer
gases.
13. Which fixture requires a trap primer?
Floor drain
Trap primers keep traps filled with water to prevent gas entry.
14. How should plastic pipes be joined?
Solvent cement or threaded fittings
Proper joining ensures leak-free connections.
15. What is the primary purpose of a backflow preventer?
To prevent contaminated water from entering the potable supply
It protects the drinking water from cross-connections.
16. What is the minimum size for a residential water heater
relief valve discharge pipe?
3/4 inch
This allows safe discharge of water under pressure.
17. How many inches above the floor should a lavatory trap arm
extend before connecting to the drain?
6 inches
This prevents siphoning and ensures proper drainage.
18. Which type of joint is commonly used with cast-iron soil
pipes?
Hub-and-spigot with lead and oakum
Traditional method providing a watertight seal in cast iron piping.
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A |
Instant Download Pdf
1. What is the minimum water pressure required at a plumbing
fixture?
30 psi
This ensures proper fixture operation and prevents backflow
issues.
2. Which pipe material is most commonly used for residential water
supply lines?
Copper
Copper is durable, corrosion-resistant, and approved for potable
water.
3. What is the maximum distance a trap can be from a vent?
5 feet
This prevents siphoning and ensures proper drainage.
4. What is the purpose of a P-trap?
To prevent sewer gases from entering a building
The water in the trap forms a seal that blocks gases.
5. Which type of valve is best for emergency shut-off of water to a
fixture?
, Ball valve
Ball valves are quick to operate and provide a full shut-off.
6. What is the required slope for horizontal drainage pipes?
1/4 inch per foot
Proper slope ensures gravity drainage and prevents clogs.
7. Which code regulates plumbing installation standards in the U.S.?
Uniform Plumbing Code (UPC)
The UPC provides consistent safety and performance
requirements.
8. What is the standard thread type for most residential plumbing
fittings?
NPT (National Pipe Thread)
NPT threads provide a tight seal for metal pipe connections.
9. What is the typical size of a water service line to a single-family
home?
3/4 inch
This is sufficient to meet most residential water demand.
10. What type of water heater requires a vent to the outside?
Gas water heater
Gas water heaters produce combustion gases that must be safely
vented.
11. Which type of pipe is commonly used for gas distribution in
residential buildings?
Black steel
Black steel is durable and compatible with natural gas and
propane.
, 12. What is the minimum height for a plumbing vent above the
roof?
6 inches
This prevents backpressure and allows proper venting of sewer
gases.
13. Which fixture requires a trap primer?
Floor drain
Trap primers keep traps filled with water to prevent gas entry.
14. How should plastic pipes be joined?
Solvent cement or threaded fittings
Proper joining ensures leak-free connections.
15. What is the primary purpose of a backflow preventer?
To prevent contaminated water from entering the potable supply
It protects the drinking water from cross-connections.
16. What is the minimum size for a residential water heater
relief valve discharge pipe?
3/4 inch
This allows safe discharge of water under pressure.
17. How many inches above the floor should a lavatory trap arm
extend before connecting to the drain?
6 inches
This prevents siphoning and ensures proper drainage.
18. Which type of joint is commonly used with cast-iron soil
pipes?
Hub-and-spigot with lead and oakum
Traditional method providing a watertight seal in cast iron piping.
