MASTER PLUMBER PRACTICE EXAM 2
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES
2025
1. What is the minimum slope required for a 3-inch horizontal drain pipe?
A. 1/4 inch per foot
B. 1/8 inch per foot
C. 1/2 inch per foot
D. Level
Rationale: According to most plumbing codes, a 3" horizontal drain line requires
a minimum slope of 1/8 inch per foot to maintain adequate flow and prevent
blockages.
2. Which type of valve is best used to regulate flow rather than just shut it off?
A. Gate valve
B. Ball valve
,C. Globe valve
D. Check valve
Rationale: Globe valves are designed to throttle and regulate flow due to their
internal structure.
3. The maximum number of fixture units allowed on a 2-inch horizontal drain is:
A. 4
B. 8
C. 10
D. 12
Rationale: Per the Uniform Plumbing Code (UPC), a 2-inch horizontal drain can
handle up to 10 fixture units.
4. Which of the following materials is approved for underground water
distribution?
A. CPVC
B. Type K Copper
C. Type M Copper
D. Galvanized Steel
Rationale: Type K copper has the thickest walls and is rated for underground
use.
5. The purpose of a trap seal is to:
,A. Prevent clogs
B. Control water pressure
C. Prevent sewer gases from entering the building
D. Increase water velocity
Rationale: Trap seals create a water barrier to block harmful sewer gases.
6. What is the minimum size of a building sewer?
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
Rationale: Most codes require a minimum 6-inch diameter for a building sewer
exiting the property.
7. A branch vent connects to:
A. The building sewer
B. The vent stack or stack vent
C. A trap directly
D. The cleanout
Rationale: A branch vent connects individual vents from fixtures to a main vent
system.
8. What is the maximum distance a trap can be from its vent for a 1½ inch pipe?
, A. 2 feet
B. 3 feet
C. 5 feet
D. 6 feet
Rationale: Per code, the maximum trap-to-vent distance for 1½" pipe is 5 feet
due to potential siphoning.
9. Which test is used to check for leaks in a DWV system before it is concealed?
A. Water pressure test
B. Flow rate test
C. Air or water test (5 ft head or 5 psi air)
D. Vacuum test
Rationale: Plumbing codes allow for an air test at 5 psi or a 10-foot head of
water to detect leaks.
10. A cleanout is required at every:
A. Horizontal run over 5 feet
B. Trap
C. Change in direction greater than 135 degrees
D. Vent stack
Rationale: Code requires cleanouts at significant changes in direction (greater
than 135°) to maintain access.
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES
2025
1. What is the minimum slope required for a 3-inch horizontal drain pipe?
A. 1/4 inch per foot
B. 1/8 inch per foot
C. 1/2 inch per foot
D. Level
Rationale: According to most plumbing codes, a 3" horizontal drain line requires
a minimum slope of 1/8 inch per foot to maintain adequate flow and prevent
blockages.
2. Which type of valve is best used to regulate flow rather than just shut it off?
A. Gate valve
B. Ball valve
,C. Globe valve
D. Check valve
Rationale: Globe valves are designed to throttle and regulate flow due to their
internal structure.
3. The maximum number of fixture units allowed on a 2-inch horizontal drain is:
A. 4
B. 8
C. 10
D. 12
Rationale: Per the Uniform Plumbing Code (UPC), a 2-inch horizontal drain can
handle up to 10 fixture units.
4. Which of the following materials is approved for underground water
distribution?
A. CPVC
B. Type K Copper
C. Type M Copper
D. Galvanized Steel
Rationale: Type K copper has the thickest walls and is rated for underground
use.
5. The purpose of a trap seal is to:
,A. Prevent clogs
B. Control water pressure
C. Prevent sewer gases from entering the building
D. Increase water velocity
Rationale: Trap seals create a water barrier to block harmful sewer gases.
6. What is the minimum size of a building sewer?
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
Rationale: Most codes require a minimum 6-inch diameter for a building sewer
exiting the property.
7. A branch vent connects to:
A. The building sewer
B. The vent stack or stack vent
C. A trap directly
D. The cleanout
Rationale: A branch vent connects individual vents from fixtures to a main vent
system.
8. What is the maximum distance a trap can be from its vent for a 1½ inch pipe?
, A. 2 feet
B. 3 feet
C. 5 feet
D. 6 feet
Rationale: Per code, the maximum trap-to-vent distance for 1½" pipe is 5 feet
due to potential siphoning.
9. Which test is used to check for leaks in a DWV system before it is concealed?
A. Water pressure test
B. Flow rate test
C. Air or water test (5 ft head or 5 psi air)
D. Vacuum test
Rationale: Plumbing codes allow for an air test at 5 psi or a 10-foot head of
water to detect leaks.
10. A cleanout is required at every:
A. Horizontal run over 5 feet
B. Trap
C. Change in direction greater than 135 degrees
D. Vent stack
Rationale: Code requires cleanouts at significant changes in direction (greater
than 135°) to maintain access.
