CSLB C36 Plumbing License Exam Prep 2025/2026 –
Study Guide & Practice Test
CSLB C36 Plumbing License Exam Prep 2025/2026
Category 1: Plumbing Code & Regulations (UPC/CPC)
1. According to the UPC, what is the minimum required size for a building sewer serving a
single-family dwelling?
A) 2 inches
B) 3 inches ✓
C) 4 inches
D) 6 inches
2. The minimum required clearance in front of a water heater is how many inches?
A) 12 inches
B) 18 inches
C) 24 inches ✓
D) 36 inches
3. What is the maximum horizontal distance a vent pipe can be from a trap weir?
A) 5 feet
B) 10 feet ✓
C) 12 feet
D) 15 feet
4. A "wet vent" is a pipe that serves as both a:
A) Waste stack and vent stack
B) Vent and waste pipe for other fixtures ✓
C) Soil pipe and storm drain
D) Stack vent and air admittance valve
5. The primary purpose of a trap is to:
A) Slow the flow of waste
B) Prevent sewer gases from entering the building ✓
C) Vent the drainage system
D) Provide a cleanout point
6. The minimum slope for a 4-inch horizontal building drain is:
A) 1/8 inch per foot
, B) 1/4 inch per foot ✓
C) 1/2 inch per foot
D) 1 inch per foot
7. A water distribution pipe carrying non-potable water must be identified by what
color?
A) Green
B) Yellow ✓
C) Red
D) Blue
8. What is the minimum required size for the drain pipe serving a standard kitchen sink?
A) 1-1/4 inch
B) 1-1/2 inch ✓
C) 2 inch
D) 3 inch
9. A "cleanout" must be installed at every change of direction greater than:
A) 22.5 degrees
B) 45 degrees ✓
C) 90 degrees
D) 135 degrees
10. The air gap for a faucet on a service sink must be at least:
A) 1 inch ✓
B) 2 inches
C) 1/2 inch
D) 3 inches
11. A relief valve on a water heater must discharge to where?
A) A nearby floor drain
B) The sanitary sewer line
C) Indirectly to the outdoors or an approved receptor ✓
D) Directly to the storm drain
12. The minimum size for a main vent stack in a two-story, single-family home is typically:
A) 1-1/4 inch
B) 1-1/2 inch
C) 3 inches ✓
D) 4 inches
, 13. Backflow prevention is required for water supply lines to a:
A) Kitchen sink
B) Lawn irrigation system ✓
C) Bathtub
D) Laundry tub
14. A "circuit vent" serves how many traps?
A) One
B) Two ✓
C) Three to eight
D) More than eight
15. The minimum required water pressure at any fixture is:
A) 10 psi
B) 15 psi ✓
C) 20 psi
D) 30 psi
Category 2: Math, Plans, and Measurements
16. To find the area of a circle, you use the formula:
A) π x r² ✓
B) 2 x π x r
C) π x d
D) L x W
17. A pipe has a rise of 1/4 inch per foot. What is the total fall over a 20-foot run?
A) 2 inches
B) 5 inches ✓
C) 10 inches
D) 20 inches
18. The volume of a cylindrical tank is calculated with the formula:
A) L x W x H
B) π x r² x h ✓
C) 2πr
D) (π x d²) / 4
19. If a water meter reads 00284 on January 1st and 00723 on February 1st, how many
cubic feet of water were used?
A) 439 ✓
, B) 539
C) 1007
D) 4390
20. You need to cut a 45-degree angle on a pipe. What is the travel (hypotenuse) for a 10-
inch offset?
A) 10 inches
B) 12.14 inches
C) 14.14 inches ✓
D) 17.32 inches
21. A blueprint scale reads 1/4" = 1'. A pipe on the drawing measures 3 inches. How long
is the actual pipe?
A) 6 feet
B) 12 feet ✓
C) 15 feet
D) 24 feet
22. The total fixture unit load for a drainage system is calculated to determine the
required:
A) Water pressure
B) Pipe size ✓
C) Number of vents
D) Water meter size
23. A 22.5-degree bend is often called a:
A) Quarter bend
B) Eighth bend ✓
C) Sixteenth bend
D) Short sweep bend
24. What is the developed length of a pipe run that has a 10-foot horizontal section and a
5-foot vertical section?
A) 10 feet
B) 11.18 feet ✓
C) 15 feet
D) 25 feet
25. Pressure is typically measured in:
A) Gallons per minute (GPM)
Study Guide & Practice Test
CSLB C36 Plumbing License Exam Prep 2025/2026
Category 1: Plumbing Code & Regulations (UPC/CPC)
1. According to the UPC, what is the minimum required size for a building sewer serving a
single-family dwelling?
A) 2 inches
B) 3 inches ✓
C) 4 inches
D) 6 inches
2. The minimum required clearance in front of a water heater is how many inches?
A) 12 inches
B) 18 inches
C) 24 inches ✓
D) 36 inches
3. What is the maximum horizontal distance a vent pipe can be from a trap weir?
A) 5 feet
B) 10 feet ✓
C) 12 feet
D) 15 feet
4. A "wet vent" is a pipe that serves as both a:
A) Waste stack and vent stack
B) Vent and waste pipe for other fixtures ✓
C) Soil pipe and storm drain
D) Stack vent and air admittance valve
5. The primary purpose of a trap is to:
A) Slow the flow of waste
B) Prevent sewer gases from entering the building ✓
C) Vent the drainage system
D) Provide a cleanout point
6. The minimum slope for a 4-inch horizontal building drain is:
A) 1/8 inch per foot
, B) 1/4 inch per foot ✓
C) 1/2 inch per foot
D) 1 inch per foot
7. A water distribution pipe carrying non-potable water must be identified by what
color?
A) Green
B) Yellow ✓
C) Red
D) Blue
8. What is the minimum required size for the drain pipe serving a standard kitchen sink?
A) 1-1/4 inch
B) 1-1/2 inch ✓
C) 2 inch
D) 3 inch
9. A "cleanout" must be installed at every change of direction greater than:
A) 22.5 degrees
B) 45 degrees ✓
C) 90 degrees
D) 135 degrees
10. The air gap for a faucet on a service sink must be at least:
A) 1 inch ✓
B) 2 inches
C) 1/2 inch
D) 3 inches
11. A relief valve on a water heater must discharge to where?
A) A nearby floor drain
B) The sanitary sewer line
C) Indirectly to the outdoors or an approved receptor ✓
D) Directly to the storm drain
12. The minimum size for a main vent stack in a two-story, single-family home is typically:
A) 1-1/4 inch
B) 1-1/2 inch
C) 3 inches ✓
D) 4 inches
, 13. Backflow prevention is required for water supply lines to a:
A) Kitchen sink
B) Lawn irrigation system ✓
C) Bathtub
D) Laundry tub
14. A "circuit vent" serves how many traps?
A) One
B) Two ✓
C) Three to eight
D) More than eight
15. The minimum required water pressure at any fixture is:
A) 10 psi
B) 15 psi ✓
C) 20 psi
D) 30 psi
Category 2: Math, Plans, and Measurements
16. To find the area of a circle, you use the formula:
A) π x r² ✓
B) 2 x π x r
C) π x d
D) L x W
17. A pipe has a rise of 1/4 inch per foot. What is the total fall over a 20-foot run?
A) 2 inches
B) 5 inches ✓
C) 10 inches
D) 20 inches
18. The volume of a cylindrical tank is calculated with the formula:
A) L x W x H
B) π x r² x h ✓
C) 2πr
D) (π x d²) / 4
19. If a water meter reads 00284 on January 1st and 00723 on February 1st, how many
cubic feet of water were used?
A) 439 ✓
, B) 539
C) 1007
D) 4390
20. You need to cut a 45-degree angle on a pipe. What is the travel (hypotenuse) for a 10-
inch offset?
A) 10 inches
B) 12.14 inches
C) 14.14 inches ✓
D) 17.32 inches
21. A blueprint scale reads 1/4" = 1'. A pipe on the drawing measures 3 inches. How long
is the actual pipe?
A) 6 feet
B) 12 feet ✓
C) 15 feet
D) 24 feet
22. The total fixture unit load for a drainage system is calculated to determine the
required:
A) Water pressure
B) Pipe size ✓
C) Number of vents
D) Water meter size
23. A 22.5-degree bend is often called a:
A) Quarter bend
B) Eighth bend ✓
C) Sixteenth bend
D) Short sweep bend
24. What is the developed length of a pipe run that has a 10-foot horizontal section and a
5-foot vertical section?
A) 10 feet
B) 11.18 feet ✓
C) 15 feet
D) 25 feet
25. Pressure is typically measured in:
A) Gallons per minute (GPM)
