PRACTICE QUESTIONS AND CORRECT
ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALES 2026 Q&A | INSTANT
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1. What is the minimum slope required for a 3-inch horizontal drain
pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 3/8 inch per foot
Proper drainage requires at least 1/4 inch per foot for 3-inch
pipes to maintain flow velocity.
2. The minimum size of a vent pipe for a 4-inch building drain is:
A. 2 inches
B. 2.5 inches
C. 3 inches
D. 4 inches
Vents must be at least half the diameter of the drain served but
not less than 1 1/4 inches.
3. What is the standard color code for potable water lines?
A. Red
B. Yellow
C. Blue
, D. Green
Blue identifies potable water in plumbing systems.
4. The maximum trap arm length for a 2-inch drain pipe is:
A. 2 feet
B. 4 feet
C. 5 feet
D. 6 feet
Per code, a 2-inch trap arm cannot exceed 5 feet before venting.
5. Which fitting is used to connect two pipes of different diameters?
A. Tee
B. Reducer coupling
C. Elbow
D. Cross
A reducer coupling allows transition between different pipe
sizes.
6. What is the purpose of a cleanout?
A. To add venting
B. To provide access for clearing blockages
C. To relieve pressure
D. To test for leaks
Cleanouts allow easy maintenance and blockage removal.
7. A backflow preventer protects against:
A. Leaks
B. Reverse flow of contaminated water
C. Pipe collapse
D. Water hammer
It ensures potable water is not contaminated by reverse flow.
, 8. The minimum depth of a water service pipe below grade in
freezing areas is:
A. 6 inches
B. 12 inches
C. Below frost line
D. 2 feet
Water lines must be buried below the local frost line to prevent
freezing.
9. Which material is not approved for hot water distribution?
A. Copper
B. PEX
C. PVC
D. CPVC
PVC cannot handle high temperatures; CPVC is used instead.
10. The function of a trap seal is to:
A. Increase flow
B. Prevent sewer gases from entering the building
C. Reduce pressure
D. Trap solids
Trap seals create a water barrier against sewer gases.
11. The main function of a relief valve is to:
A. Increase water pressure
B. Prevent excessive pressure in the system
C. Direct flow
D. Reduce water temperature
Relief valves protect pipes and appliances from overpressure
damage.
12. A vent stack must terminate at least how far above the roof?
A. 6 inches