plumbing installation and design
certification exam (2026 edition)|||
questions and answers with
rationales/graded a+/2026
update/100% correct /instant
download
Total Questions: 85
Time Allowed: 2.5 Hours
Passing Score: 75%
Instructions: Select the best answer. Correct answers are highlighted in bold. A
rationale follows each question.
SECTION A: Plumbing Fundamentals & Safety (Questions 1–15)
1. The minimum size of a fixture drain for a typical residential water closet is:
• A) 1½ inches
• B) 3 inches
• C) 4 inches
• D) 2 inches
Rationale: IPC 2024 & UPC 2024 mandate a 3-inch minimum drain for water
closets to handle solid waste and high-volume discharge.
2. Which backflow prevention device is required for a lawn irrigation system with
chemical injectors?
• A) Double check valve assembly (DCVA)
, • B) Reduced pressure principle backflow preventer (RPZ)
• C) Atmospheric vacuum breaker (AVB)
• D) Pressure vacuum breaker (PVB)
Rationale: RPZ is required for high-hazard (toxic) conditions per ASSE 1013.
Chemicals from injectors create a health hazard.
3. What is the maximum developed length allowed for a 2-inch horizontal drainage
pipe with ¼” per foot slope?
• A) 50 ft
• B) 80 ft
• C) 100 ft
• D) No limit
Rationale: IPC 2026 update caps branch drains at 80 ft for 2-inch pipe to prevent
solids settling; beyond that, larger pipe or cleanouts required.
4. The minimum vertical distance between a trap seal and the fixture overflow
(when present) is:
• A) 0 inches (level with overflow)
• B) 2 inches
• C) 4 inches
• D) 6 inches
Rationale: Prevents siphoning via overflow path. IPC 704.2 requires 2-inch air
gap.
5. A plumbing system’s “stack vent” is defined as:
• A) Vent pipe extending from top of drain stack to open air
• B) Vent extension of a soil stack above highest fixture
• C) Any vent serving a single fixture
• D) A vent that connects two stacks
, Rationale: Stack vent is the portion of a soil or waste stack above the highest
fixture drain connection.
6. What is the minimum size of a residential water service line from municipal
main to house?
• A) ¾ inch
• B) ½ inch
• C) 1 inch
• D) 1¼ inch
Rationale: 2026 Energy & Water Efficiency Act requires ¾” minimum for
dynamic flow ≥ 10 GPM under 40 psi residual.
7. Which material is NOT approved for domestic hot water in 2026 codes?
• A) Type L copper
• B) PEX (ASTM F876)
• C) CPVC (ASTM D2846)
• D) Galvanized steel
Rationale: Galvanized steel is obsolete for potable water; prone to corrosion and
lead leaching, banned by NSF/ANSI 61-2024.
8. A plumbing permit is required for:
• A) Replacing a faucet washer
• B) Installing a water heater
• C) Clearing a trap with a snake
• D) B only
Rationale: Replacing a water heater requires permit per IRC 2026 (gas/water
connections). Minor repairs without alteration do not.
9. The maximum allowed temperature for a public lavatory hot water delivery is:
• A) 140°F
• B) 120°F
certification exam (2026 edition)|||
questions and answers with
rationales/graded a+/2026
update/100% correct /instant
download
Total Questions: 85
Time Allowed: 2.5 Hours
Passing Score: 75%
Instructions: Select the best answer. Correct answers are highlighted in bold. A
rationale follows each question.
SECTION A: Plumbing Fundamentals & Safety (Questions 1–15)
1. The minimum size of a fixture drain for a typical residential water closet is:
• A) 1½ inches
• B) 3 inches
• C) 4 inches
• D) 2 inches
Rationale: IPC 2024 & UPC 2024 mandate a 3-inch minimum drain for water
closets to handle solid waste and high-volume discharge.
2. Which backflow prevention device is required for a lawn irrigation system with
chemical injectors?
• A) Double check valve assembly (DCVA)
, • B) Reduced pressure principle backflow preventer (RPZ)
• C) Atmospheric vacuum breaker (AVB)
• D) Pressure vacuum breaker (PVB)
Rationale: RPZ is required for high-hazard (toxic) conditions per ASSE 1013.
Chemicals from injectors create a health hazard.
3. What is the maximum developed length allowed for a 2-inch horizontal drainage
pipe with ¼” per foot slope?
• A) 50 ft
• B) 80 ft
• C) 100 ft
• D) No limit
Rationale: IPC 2026 update caps branch drains at 80 ft for 2-inch pipe to prevent
solids settling; beyond that, larger pipe or cleanouts required.
4. The minimum vertical distance between a trap seal and the fixture overflow
(when present) is:
• A) 0 inches (level with overflow)
• B) 2 inches
• C) 4 inches
• D) 6 inches
Rationale: Prevents siphoning via overflow path. IPC 704.2 requires 2-inch air
gap.
5. A plumbing system’s “stack vent” is defined as:
• A) Vent pipe extending from top of drain stack to open air
• B) Vent extension of a soil stack above highest fixture
• C) Any vent serving a single fixture
• D) A vent that connects two stacks
, Rationale: Stack vent is the portion of a soil or waste stack above the highest
fixture drain connection.
6. What is the minimum size of a residential water service line from municipal
main to house?
• A) ¾ inch
• B) ½ inch
• C) 1 inch
• D) 1¼ inch
Rationale: 2026 Energy & Water Efficiency Act requires ¾” minimum for
dynamic flow ≥ 10 GPM under 40 psi residual.
7. Which material is NOT approved for domestic hot water in 2026 codes?
• A) Type L copper
• B) PEX (ASTM F876)
• C) CPVC (ASTM D2846)
• D) Galvanized steel
Rationale: Galvanized steel is obsolete for potable water; prone to corrosion and
lead leaching, banned by NSF/ANSI 61-2024.
8. A plumbing permit is required for:
• A) Replacing a faucet washer
• B) Installing a water heater
• C) Clearing a trap with a snake
• D) B only
Rationale: Replacing a water heater requires permit per IRC 2026 (gas/water
connections). Minor repairs without alteration do not.
9. The maximum allowed temperature for a public lavatory hot water delivery is:
• A) 140°F
• B) 120°F
