Missouri plumbing plans examiner — st.
Charles exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. What is the minimum slope 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. 1 inch per foot
Answer: B
Minimum slope for 3-inch and smaller horizontal drains is 1/4 inch
per foot per standard plumbing code requirements.
2. A vent pipe primarily functions to:
A. Carry wastewater
B. Increase water pressure
C. Prevent trap siphonage
, D. Reduce pipe size
Answer: C
Vents protect trap seals by equalizing pressure in the drainage
system.
3. The minimum trap seal depth is typically:
A. 1 inch
B. 2 inches
C. 3 inches
D. 4 inches
Answer: B
Most plumbing codes require a 2-inch trap seal minimum for fixture
protection.
4. What is the purpose of a cleanout?
A. Increase flow velocity
B. Provide access for cleaning drains
C. Vent the system
D. Reduce pipe friction
Answer: B
Cleanouts allow access for removing blockages and maintenance.
5. A water hammer arrester is used to:
A. Increase flow rate
B. Prevent pressure surges
C. Reduce pipe size
, D. Heat water
Answer: B
Water hammer arresters absorb shock from sudden valve closure.
6. Minimum fixture vent size is generally:
A. 1/4 inch
B. 1/2 inch
C. 1-1/4 inch
D. 3 inches
Answer: C
Most codes require a minimum 1-1/4 inch vent pipe size.
7. The primary purpose of a trap is to:
A. Increase drainage speed
B. Prevent sewer gas entry
C. Store water
D. Vent pipes
Answer: B
Traps maintain a water seal that blocks sewer gases.
8. The maximum distance between a trap and vent depends on:
A. Pipe color
B. Pipe diameter
C. Water pressure
D. Building height
, Answer: B
Trap arm length is limited by pipe diameter and slope requirements.
9. A stack vent is:
A. A drainage pipe
B. A vertical continuation of a soil stack above fixtures
C. A trap seal
D. A water supply line
Answer: B
Stack vents extend vertically to relieve pressure in drainage systems.
10. Air admittance valves are:
A. Mechanical vents allowing air into drainage systems
B. Water pumps
C. Drainage pipes
D. Backflow preventers
Answer: A
AAVs allow air into the system to prevent siphonage without exterior
venting.
11. The minimum slope for 4-inch horizontal drain piping is:
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/16 inch per foot
D. 1 inch per foot
Charles exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. What is the minimum slope 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. 1 inch per foot
Answer: B
Minimum slope for 3-inch and smaller horizontal drains is 1/4 inch
per foot per standard plumbing code requirements.
2. A vent pipe primarily functions to:
A. Carry wastewater
B. Increase water pressure
C. Prevent trap siphonage
, D. Reduce pipe size
Answer: C
Vents protect trap seals by equalizing pressure in the drainage
system.
3. The minimum trap seal depth is typically:
A. 1 inch
B. 2 inches
C. 3 inches
D. 4 inches
Answer: B
Most plumbing codes require a 2-inch trap seal minimum for fixture
protection.
4. What is the purpose of a cleanout?
A. Increase flow velocity
B. Provide access for cleaning drains
C. Vent the system
D. Reduce pipe friction
Answer: B
Cleanouts allow access for removing blockages and maintenance.
5. A water hammer arrester is used to:
A. Increase flow rate
B. Prevent pressure surges
C. Reduce pipe size
, D. Heat water
Answer: B
Water hammer arresters absorb shock from sudden valve closure.
6. Minimum fixture vent size is generally:
A. 1/4 inch
B. 1/2 inch
C. 1-1/4 inch
D. 3 inches
Answer: C
Most codes require a minimum 1-1/4 inch vent pipe size.
7. The primary purpose of a trap is to:
A. Increase drainage speed
B. Prevent sewer gas entry
C. Store water
D. Vent pipes
Answer: B
Traps maintain a water seal that blocks sewer gases.
8. The maximum distance between a trap and vent depends on:
A. Pipe color
B. Pipe diameter
C. Water pressure
D. Building height
, Answer: B
Trap arm length is limited by pipe diameter and slope requirements.
9. A stack vent is:
A. A drainage pipe
B. A vertical continuation of a soil stack above fixtures
C. A trap seal
D. A water supply line
Answer: B
Stack vents extend vertically to relieve pressure in drainage systems.
10. Air admittance valves are:
A. Mechanical vents allowing air into drainage systems
B. Water pumps
C. Drainage pipes
D. Backflow preventers
Answer: A
AAVs allow air into the system to prevent siphonage without exterior
venting.
11. The minimum slope for 4-inch horizontal drain piping is:
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/16 inch per foot
D. 1 inch per foot
