Master Plumber Licensing Exam
Questions And Correct Answers
1. The minimum slope required for a 3-inch horizontal drain pipe is:
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
Proper slope ensures gravity drainage and prevents standing water in the
pipe.
2. Which type of valve is typically used to control water flow in a
domestic hot water system?
A. Gate valve
B. Check valve
C. Ball valve
D. Butterfly valve
Ball valves provide reliable shutoff and are easy to operate.
3. What is the primary purpose of a plumbing vent?
A. Reduce water pressure
B. Filter debris
C. Allow air into the drainage system to prevent siphoning of
traps
D. Heat water in the system
Vents maintain proper pressure in drainage lines, preventing traps from
being emptied.
4. A backflow preventer is required when:
A. Connecting a water heater
B. There is a potential for cross-connection with contaminated
water
, C. Installing a new faucet
D. Replacing a drain pipe
This prevents contamination of the potable water supply.
5. What is the typical maximum spacing for supports on a 2-inch PVC drain
line?
A. 2 feet
B. 3 feet
C. 4 feet
D. 6 feet
Proper support prevents sagging and ensures proper drainage.
6. The term "DWV" in plumbing stands for:
A. Direct Water Valve
B. Domestic Water Vent
C. Drain, Waste, and Vent
D. Dual Water Valve
DWV systems manage all non-pressurized plumbing flows in a building.
7. Which material is most commonly used for underground water supply
lines?
A. Copper
B. PEX
C. Cast iron
D. Galvanized steel
PEX is flexible, resistant to corrosion, and easy to install underground.
8. Which fixture requires a trap?
A. Water heater
B. Sink
C. Water meter
D. Boiler
Traps prevent sewer gases from entering living spaces.
9. What is the purpose of a pressure-reducing valve?
, A. Increase flow
B. Lower incoming water pressure to safe levels
C. Divert water
D. Measure water usage
High pressure can damage plumbing fixtures and appliances.
10. The maximum distance a water closet trap arm can extend without
venting is:
A. 12 inches
B. 24 inches
C. 30 inches
D. 36 inches
Venting prevents siphoning and ensures proper trap function.
11. What is the standard water supply pipe size for a residential kitchen
sink?
A. 1/2 inch
B. 3/4 inch
C. 1/2 inch
D. 3/8 inch
This size provides sufficient flow without excessive pressure loss.
12. A sewage ejector pump is required when:
A. The building is above the main sewer
B. The plumbing fixtures are below the level of the main sewer line
C. Connecting a water heater
D. Installing a gas line
It pumps wastewater uphill to connect with the gravity sewer.
13. What is the minimum distance between a water heater and
combustible materials?
A. 6 inches
B. 12 inches
C. 18 inches
Questions And Correct Answers
1. The minimum slope required for a 3-inch horizontal drain pipe is:
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
Proper slope ensures gravity drainage and prevents standing water in the
pipe.
2. Which type of valve is typically used to control water flow in a
domestic hot water system?
A. Gate valve
B. Check valve
C. Ball valve
D. Butterfly valve
Ball valves provide reliable shutoff and are easy to operate.
3. What is the primary purpose of a plumbing vent?
A. Reduce water pressure
B. Filter debris
C. Allow air into the drainage system to prevent siphoning of
traps
D. Heat water in the system
Vents maintain proper pressure in drainage lines, preventing traps from
being emptied.
4. A backflow preventer is required when:
A. Connecting a water heater
B. There is a potential for cross-connection with contaminated
water
, C. Installing a new faucet
D. Replacing a drain pipe
This prevents contamination of the potable water supply.
5. What is the typical maximum spacing for supports on a 2-inch PVC drain
line?
A. 2 feet
B. 3 feet
C. 4 feet
D. 6 feet
Proper support prevents sagging and ensures proper drainage.
6. The term "DWV" in plumbing stands for:
A. Direct Water Valve
B. Domestic Water Vent
C. Drain, Waste, and Vent
D. Dual Water Valve
DWV systems manage all non-pressurized plumbing flows in a building.
7. Which material is most commonly used for underground water supply
lines?
A. Copper
B. PEX
C. Cast iron
D. Galvanized steel
PEX is flexible, resistant to corrosion, and easy to install underground.
8. Which fixture requires a trap?
A. Water heater
B. Sink
C. Water meter
D. Boiler
Traps prevent sewer gases from entering living spaces.
9. What is the purpose of a pressure-reducing valve?
, A. Increase flow
B. Lower incoming water pressure to safe levels
C. Divert water
D. Measure water usage
High pressure can damage plumbing fixtures and appliances.
10. The maximum distance a water closet trap arm can extend without
venting is:
A. 12 inches
B. 24 inches
C. 30 inches
D. 36 inches
Venting prevents siphoning and ensures proper trap function.
11. What is the standard water supply pipe size for a residential kitchen
sink?
A. 1/2 inch
B. 3/4 inch
C. 1/2 inch
D. 3/8 inch
This size provides sufficient flow without excessive pressure loss.
12. A sewage ejector pump is required when:
A. The building is above the main sewer
B. The plumbing fixtures are below the level of the main sewer line
C. Connecting a water heater
D. Installing a gas line
It pumps wastewater uphill to connect with the gravity sewer.
13. What is the minimum distance between a water heater and
combustible materials?
A. 6 inches
B. 12 inches
C. 18 inches
