Texas Master Plumber Exam Verified Questions,
Correct Answers, and Detailed Explanations for
Science Students||Already Graded A+
1. Minimum slope for horizontal drainage piping 2½ inches or
smaller is:
A. 1/16 inch per foot
B. 1/4 inch per foot
C. 1/8 inch per foot
D. 1/2 inch per foot
Small-diameter drains require 1/4" per foot to maintain scouring
velocity.
2. A cleanout is required at the base of each:
A. Horizontal branch
B. Vertical stack
C. Fixture drain
D. Trap arm
Cleanouts at stack bases allow access for maintenance and blockage
removal.
3. The minimum trap seal depth is:
A. 1 inch
B. 2 inches
C. 3 inches
D. 4 inches
Trap seals must be deep enough (2–4 inches) to prevent sewer gas
entry.
,4. What is the minimum size for a water service to a single-family
dwelling?
A. 1/2 inch
B. 3/4 inch
C. 1 inch
D. 1¼ inch
Standard residential services are typically 3/4" minimum.
5. The maximum developed length of a trap arm depends on:
A. Pipe material only
B. Pipe diameter and slope
C. Fixture type only
D. Water pressure
Trap arm limits prevent siphoning and depend on size and grade.
6. Which fitting is prohibited for drainage direction changes?
A. Long sweep
B. Sanitary tee on its back
C. Combination wye
D. 45-degree elbow
A sanitary tee cannot be used horizontally because it restricts flow.
7. The minimum vent size for a building drain is:
A. 1 inch
B. 1¼ inches
C. 1½ inches
D. 2 inches
Vents must be large enough to prevent frost closure and maintain
airflow.
, 8. What is the maximum temperature for residential hot water
delivery?
A. 110°F
B. 115°F
C. 120°F
D. 140°F
120°F reduces scald risk while maintaining sanitation.
9. A backflow preventer protects against:
A. Water hammer
B. Contamination of potable water
C. Low pressure
D. Pipe corrosion
Backflow devices prevent reversal of contaminated water into supply.
10. Minimum burial depth for water service in Texas (typical code
practice):
A. 6 inches
B. 12 inches
C. 18 inches
D. 24 inches
Depth protects against damage and temperature extremes.
11. What fixture unit value is typically assigned to a water closet
(tank type)?
A. 2
B. 3
C. 4
Correct Answers, and Detailed Explanations for
Science Students||Already Graded A+
1. Minimum slope for horizontal drainage piping 2½ inches or
smaller is:
A. 1/16 inch per foot
B. 1/4 inch per foot
C. 1/8 inch per foot
D. 1/2 inch per foot
Small-diameter drains require 1/4" per foot to maintain scouring
velocity.
2. A cleanout is required at the base of each:
A. Horizontal branch
B. Vertical stack
C. Fixture drain
D. Trap arm
Cleanouts at stack bases allow access for maintenance and blockage
removal.
3. The minimum trap seal depth is:
A. 1 inch
B. 2 inches
C. 3 inches
D. 4 inches
Trap seals must be deep enough (2–4 inches) to prevent sewer gas
entry.
,4. What is the minimum size for a water service to a single-family
dwelling?
A. 1/2 inch
B. 3/4 inch
C. 1 inch
D. 1¼ inch
Standard residential services are typically 3/4" minimum.
5. The maximum developed length of a trap arm depends on:
A. Pipe material only
B. Pipe diameter and slope
C. Fixture type only
D. Water pressure
Trap arm limits prevent siphoning and depend on size and grade.
6. Which fitting is prohibited for drainage direction changes?
A. Long sweep
B. Sanitary tee on its back
C. Combination wye
D. 45-degree elbow
A sanitary tee cannot be used horizontally because it restricts flow.
7. The minimum vent size for a building drain is:
A. 1 inch
B. 1¼ inches
C. 1½ inches
D. 2 inches
Vents must be large enough to prevent frost closure and maintain
airflow.
, 8. What is the maximum temperature for residential hot water
delivery?
A. 110°F
B. 115°F
C. 120°F
D. 140°F
120°F reduces scald risk while maintaining sanitation.
9. A backflow preventer protects against:
A. Water hammer
B. Contamination of potable water
C. Low pressure
D. Pipe corrosion
Backflow devices prevent reversal of contaminated water into supply.
10. Minimum burial depth for water service in Texas (typical code
practice):
A. 6 inches
B. 12 inches
C. 18 inches
D. 24 inches
Depth protects against damage and temperature extremes.
11. What fixture unit value is typically assigned to a water closet
(tank type)?
A. 2
B. 3
C. 4
