NCCER Plumbing Level 2 Certification Practice
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Actual Past Papers 150 Most Examined
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1. A plumber is installing a drainage system in a commercial building. Which
component is primarily used to prevent sewer gases from entering the
occupied space?
A. Cleanout
B. Trap
C. Vent stack
D. Backflow preventer
✔ B. Trap
Explanation: A trap retains water to create a seal that blocks sewer gases
from entering the building, which is its primary function.
2. What is the minimum slope required for a 3-inch horizontal drainage pipe
according to standard plumbing codes?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
✔ B. 1/8 inch per foot
Explanation: For pipes 3 inches and larger, the minimum slope is typically
1/8 inch per foot to maintain proper flow velocity.
3. Which tool is used to cut threads on the outside of a pipe?
A. Pipe wrench
B. Reamer
, C. Die
D. Tap
✔ C. Die
Explanation: A die is used to cut external threads on pipes, enabling
proper fitting connections.
4. A plumber notices water hammer in a residential system. What is the most
effective solution?
A. Increase pipe diameter
B. Install a pressure regulator
C. Install water hammer arrestors
D. Replace all fittings
✔ C. Install water hammer arrestors
Explanation: Water hammer arrestors absorb shock waves caused by
sudden valve closure, eliminating noise and pipe stress.
5. Which material is most commonly used for DWV systems in modern
residential construction?
A. Copper
B. PVC
C. Galvanized steel
D. Cast iron
✔ B. PVC
Explanation: PVC is widely used due to its corrosion resistance,
affordability, and ease of installation.
6. What is the purpose of a cleanout in a plumbing system?
A. Increase water pressure
B. Allow system ventilation
C. Provide access for cleaning pipes
D. Prevent backflow
✔ C. Provide access for cleaning pipes
Explanation: Cleanouts allow plumbers to remove blockages and maintain
drainage systems efficiently.
,7. Which fitting is used to connect two pipes at a 90-degree angle?
A. Coupling
B. Tee
C. Elbow
D. Reducer
✔ C. Elbow
Explanation: Elbows are specifically designed to change pipe direction,
commonly at 90 degrees.
8. In a venting system, what is the function of a vent stack?
A. Carry waste water
B. Equalize pressure
C. Store water
D. Increase flow rate
✔ B. Equalize pressure
Explanation: Vent stacks maintain atmospheric pressure within the
drainage system, preventing siphoning of traps.
9. Which device prevents contamination of potable water due to backflow?
A. Trap
B. Air gap
C. Valve
D. Pump
✔ B. Air gap
Explanation: An air gap provides a physical separation that prevents
backflow contamination.
10.What type of pipe is best suited for underground water service lines?
A. PVC Schedule 40
B. PEX
C. Copper Type M
D. Cast iron
✔ A. PVC Schedule 40
, Explanation: PVC Schedule 40 is durable and resistant to corrosion,
making it suitable for underground use.
11.What is the primary purpose of flux in soldering copper pipes?
A. Strengthen joint
B. Clean surfaces
C. Increase heat
D. Seal leaks
✔ B. Clean surfaces
Explanation: Flux removes oxidation and allows solder to bond effectively
to metal surfaces.
12.Which valve is used to completely stop or allow flow in a system?
A. Globe valve
B. Check valve
C. Gate valve
D. Relief valve
✔ C. Gate valve
Explanation: Gate valves are designed for full open or closed positions,
not for throttling.
13.What is the standard pressure range for residential water systems?
A. 10–20 psi
B. 20–40 psi
C. 40–80 psi
D. 80–120 psi
✔ C. 40–80 psi
Explanation: This range ensures adequate water flow without damaging
plumbing fixtures.
14.Which pipe joining method uses heat to melt and fuse materials?
A. Threading
B. Solvent welding
C. Compression fitting
Latest 2025-2026 Update Fast Reviewed From
Actual Past Papers 150 Most Examined
Questions And 100% Verified Answers| A+
Grade Q&A | Instant Download Pdf
1. A plumber is installing a drainage system in a commercial building. Which
component is primarily used to prevent sewer gases from entering the
occupied space?
A. Cleanout
B. Trap
C. Vent stack
D. Backflow preventer
✔ B. Trap
Explanation: A trap retains water to create a seal that blocks sewer gases
from entering the building, which is its primary function.
2. What is the minimum slope required for a 3-inch horizontal drainage pipe
according to standard plumbing codes?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
✔ B. 1/8 inch per foot
Explanation: For pipes 3 inches and larger, the minimum slope is typically
1/8 inch per foot to maintain proper flow velocity.
3. Which tool is used to cut threads on the outside of a pipe?
A. Pipe wrench
B. Reamer
, C. Die
D. Tap
✔ C. Die
Explanation: A die is used to cut external threads on pipes, enabling
proper fitting connections.
4. A plumber notices water hammer in a residential system. What is the most
effective solution?
A. Increase pipe diameter
B. Install a pressure regulator
C. Install water hammer arrestors
D. Replace all fittings
✔ C. Install water hammer arrestors
Explanation: Water hammer arrestors absorb shock waves caused by
sudden valve closure, eliminating noise and pipe stress.
5. Which material is most commonly used for DWV systems in modern
residential construction?
A. Copper
B. PVC
C. Galvanized steel
D. Cast iron
✔ B. PVC
Explanation: PVC is widely used due to its corrosion resistance,
affordability, and ease of installation.
6. What is the purpose of a cleanout in a plumbing system?
A. Increase water pressure
B. Allow system ventilation
C. Provide access for cleaning pipes
D. Prevent backflow
✔ C. Provide access for cleaning pipes
Explanation: Cleanouts allow plumbers to remove blockages and maintain
drainage systems efficiently.
,7. Which fitting is used to connect two pipes at a 90-degree angle?
A. Coupling
B. Tee
C. Elbow
D. Reducer
✔ C. Elbow
Explanation: Elbows are specifically designed to change pipe direction,
commonly at 90 degrees.
8. In a venting system, what is the function of a vent stack?
A. Carry waste water
B. Equalize pressure
C. Store water
D. Increase flow rate
✔ B. Equalize pressure
Explanation: Vent stacks maintain atmospheric pressure within the
drainage system, preventing siphoning of traps.
9. Which device prevents contamination of potable water due to backflow?
A. Trap
B. Air gap
C. Valve
D. Pump
✔ B. Air gap
Explanation: An air gap provides a physical separation that prevents
backflow contamination.
10.What type of pipe is best suited for underground water service lines?
A. PVC Schedule 40
B. PEX
C. Copper Type M
D. Cast iron
✔ A. PVC Schedule 40
, Explanation: PVC Schedule 40 is durable and resistant to corrosion,
making it suitable for underground use.
11.What is the primary purpose of flux in soldering copper pipes?
A. Strengthen joint
B. Clean surfaces
C. Increase heat
D. Seal leaks
✔ B. Clean surfaces
Explanation: Flux removes oxidation and allows solder to bond effectively
to metal surfaces.
12.Which valve is used to completely stop or allow flow in a system?
A. Globe valve
B. Check valve
C. Gate valve
D. Relief valve
✔ C. Gate valve
Explanation: Gate valves are designed for full open or closed positions,
not for throttling.
13.What is the standard pressure range for residential water systems?
A. 10–20 psi
B. 20–40 psi
C. 40–80 psi
D. 80–120 psi
✔ C. 40–80 psi
Explanation: This range ensures adequate water flow without damaging
plumbing fixtures.
14.Which pipe joining method uses heat to melt and fuse materials?
A. Threading
B. Solvent welding
C. Compression fitting
