ARKANSAS MASTER PLUMBER EXAM (PDF) | 2026
QUESTIONS & ANSWERS + RATIONALES | STUDY GUIDE |
100% CORRECT
1. Which of the following best describes the primary purpose of a plumbing trap in a drainage
system?
A) To increase water pressure at the fixture outlet
B) To prevent sewer gases from entering an occupied building
C) To increase the velocity of wastewater flow
D) To reduce the temperature of wastewater before discharge
Correct Answer: To prevent sewer gases from entering an occupied building
Rationale: A plumbing trap retains a water seal that blocks sewer gases and odors from entering
the occupied portion of a building while still allowing wastewater to drain. It does not increase
water pressure, accelerate flow, or reduce wastewater temperature. Trap seals are protected by
proper venting and must maintain a minimum depth per the Arkansas Plumbing Code.
2. What is the primary function of a plumbing vent system?
A) To supply potable water to fixtures
B) To maintain proper air pressure within the drainage system
C) To increase water temperature for sanitation
D) To filter wastewater before it enters the sewer
Correct Answer: To maintain proper air pressure within the drainage system
Rationale: Venting allows air to enter and leave the drainage system, protecting trap seals and
permitting wastewater to flow properly. Vents do not supply potable water, heat water, or filter
waste. Without adequate venting, negative pressure can siphon trap seals and allow sewer gas
into the building.
3. According to the Arkansas Plumbing Code, what is the minimum slope required for a 3-inch
horizontal drain pipe carrying wastewater?
A) 1/8 inch per foot
B) 1/4 inch per foot
C) 1/2 inch per foot
D) 1 inch per foot
Correct Answer: 1/4 inch per foot
Rationale: The 2018 Arkansas Plumbing Code requires a minimum slope of 1/4 inch per foot for
DWV pipes 3 inches and larger to ensure proper drainage. Smaller pipes may require 1/8 inch
per foot in some configurations, but 3-inch and larger pipes generally need 1/4 inch per foot.
Insufficient slope allows solids to settle and can lead to blockages.
,4. In an isometric DWV riser diagram, which color is conventionally used to identify vent piping?
A) Red
B) Green
C) Blue
D) Yellow
Correct Answer: Blue
Rationale: The Arkansas Plumbing Code recommends blue to denote vent piping on isometric
drawings, distinguishing it from drain lines, which are shown in red. Green is sometimes used for
water supply lines. Consistent color coding helps code officials and inspectors quickly interpret
the drawing.
5. What is the purpose of a cleanout in a drainage system?
A) To increase water pressure in the system
B) To provide access for cleaning drainage piping
C) To prevent water hammer during operation
D) To supply air to a fixture trap
Correct Answer: To provide access for cleaning drainage piping
Rationale: Cleanouts provide access points for drain-cleaning equipment and maintenance,
allowing blockages to be cleared without dismantling the piping system. They do not increase
water pressure, prevent water hammer, or supply air to fixtures. The Arkansas Plumbing Code
specifies maximum distances between cleanouts and at changes in direction.
6. Why are drainage pipes installed with a slope?
A) To increase water pressure within the pipe
B) To promote gravity drainage of wastewater
C) To prevent corrosion of the pipe interior
D) To eliminate the need for venting
Correct Answer: To promote gravity drainage of wastewater
Rationale: Drainage systems rely primarily on gravity, so proper slope allows wastewater to flow
toward the sewer or disposal point. Slope does not increase pressure, prevent corrosion, or
eliminate venting requirements. Inadequate slope can cause solids to accumulate and result in
frequent blockages.
7. What may happen if a drainage pipe has insufficient slope?
A) Water pressure increases significantly
B) Solids may accumulate in the pipe
C) Ventilation of the system improves
D) Trap seals become stronger
Correct Answer: Solids may accumulate in the pipe
, Rationale: Insufficient slope reduces flow velocity, allowing solids to settle and accumulate in
the pipe, which can lead to blockages. Adequate slope maintains a scouring velocity that keeps
solids suspended. Ventilation and trap seal strength are not improved by inadequate slope.
8. According to the 2018 Arkansas Plumbing Code, how many fixture units are assigned to a water
closet (toilet) for water demand calculations?
A) 1.0
B) 1.5
C) 2.0
D) 3.0
Correct Answer: 1.5
Rationale: The 2018 Arkansas Plumbing Code lists a water closet as 1.5 fixture units for water
demand calculations. This value is used in Appendix E to determine total fixture unit loads for
sizing water supply systems. Accurate fixture unit values ensure that water supply piping is sized
appropriately for the building's demand.
9. When sizing a water supply branch pipe using the Hazen-Williams equation, which factor
represents the pipe's roughness?
A) C-factor
B) K-factor
C) F-factor
D) R-factor
Correct Answer: C-factor
Rationale: The C-factor (Hazen-Williams coefficient) quantifies pipe roughness; higher values
indicate smoother pipe material, resulting in less friction loss. New copper pipe commonly uses a
C-value of 150. The K-factor, F-factor, and R-factor are not used in the Hazen-Williams
equation for water supply sizing.
10. The Hazen-Williams coefficient (C) for new copper pipe used in water supply calculations is:
A) 100
B) 120
C) 130
D) 150
Correct Answer: 150
Rationale: New copper pipe commonly uses a C-value of 150 for Hazen-Williams calculations,
reflecting its relatively smooth interior surface. Lower C-values indicate rougher pipe and greater
friction loss. Using the correct C-value ensures accurate water supply sizing and pressure
calculations.
11. What is the minimum required size for a water service pipe from the street to the water
distribution system in a single-family dwelling, according to the Arkansas Plumbing Code?
QUESTIONS & ANSWERS + RATIONALES | STUDY GUIDE |
100% CORRECT
1. Which of the following best describes the primary purpose of a plumbing trap in a drainage
system?
A) To increase water pressure at the fixture outlet
B) To prevent sewer gases from entering an occupied building
C) To increase the velocity of wastewater flow
D) To reduce the temperature of wastewater before discharge
Correct Answer: To prevent sewer gases from entering an occupied building
Rationale: A plumbing trap retains a water seal that blocks sewer gases and odors from entering
the occupied portion of a building while still allowing wastewater to drain. It does not increase
water pressure, accelerate flow, or reduce wastewater temperature. Trap seals are protected by
proper venting and must maintain a minimum depth per the Arkansas Plumbing Code.
2. What is the primary function of a plumbing vent system?
A) To supply potable water to fixtures
B) To maintain proper air pressure within the drainage system
C) To increase water temperature for sanitation
D) To filter wastewater before it enters the sewer
Correct Answer: To maintain proper air pressure within the drainage system
Rationale: Venting allows air to enter and leave the drainage system, protecting trap seals and
permitting wastewater to flow properly. Vents do not supply potable water, heat water, or filter
waste. Without adequate venting, negative pressure can siphon trap seals and allow sewer gas
into the building.
3. According to the Arkansas Plumbing Code, what is the minimum slope required for a 3-inch
horizontal drain pipe carrying wastewater?
A) 1/8 inch per foot
B) 1/4 inch per foot
C) 1/2 inch per foot
D) 1 inch per foot
Correct Answer: 1/4 inch per foot
Rationale: The 2018 Arkansas Plumbing Code requires a minimum slope of 1/4 inch per foot for
DWV pipes 3 inches and larger to ensure proper drainage. Smaller pipes may require 1/8 inch
per foot in some configurations, but 3-inch and larger pipes generally need 1/4 inch per foot.
Insufficient slope allows solids to settle and can lead to blockages.
,4. In an isometric DWV riser diagram, which color is conventionally used to identify vent piping?
A) Red
B) Green
C) Blue
D) Yellow
Correct Answer: Blue
Rationale: The Arkansas Plumbing Code recommends blue to denote vent piping on isometric
drawings, distinguishing it from drain lines, which are shown in red. Green is sometimes used for
water supply lines. Consistent color coding helps code officials and inspectors quickly interpret
the drawing.
5. What is the purpose of a cleanout in a drainage system?
A) To increase water pressure in the system
B) To provide access for cleaning drainage piping
C) To prevent water hammer during operation
D) To supply air to a fixture trap
Correct Answer: To provide access for cleaning drainage piping
Rationale: Cleanouts provide access points for drain-cleaning equipment and maintenance,
allowing blockages to be cleared without dismantling the piping system. They do not increase
water pressure, prevent water hammer, or supply air to fixtures. The Arkansas Plumbing Code
specifies maximum distances between cleanouts and at changes in direction.
6. Why are drainage pipes installed with a slope?
A) To increase water pressure within the pipe
B) To promote gravity drainage of wastewater
C) To prevent corrosion of the pipe interior
D) To eliminate the need for venting
Correct Answer: To promote gravity drainage of wastewater
Rationale: Drainage systems rely primarily on gravity, so proper slope allows wastewater to flow
toward the sewer or disposal point. Slope does not increase pressure, prevent corrosion, or
eliminate venting requirements. Inadequate slope can cause solids to accumulate and result in
frequent blockages.
7. What may happen if a drainage pipe has insufficient slope?
A) Water pressure increases significantly
B) Solids may accumulate in the pipe
C) Ventilation of the system improves
D) Trap seals become stronger
Correct Answer: Solids may accumulate in the pipe
, Rationale: Insufficient slope reduces flow velocity, allowing solids to settle and accumulate in
the pipe, which can lead to blockages. Adequate slope maintains a scouring velocity that keeps
solids suspended. Ventilation and trap seal strength are not improved by inadequate slope.
8. According to the 2018 Arkansas Plumbing Code, how many fixture units are assigned to a water
closet (toilet) for water demand calculations?
A) 1.0
B) 1.5
C) 2.0
D) 3.0
Correct Answer: 1.5
Rationale: The 2018 Arkansas Plumbing Code lists a water closet as 1.5 fixture units for water
demand calculations. This value is used in Appendix E to determine total fixture unit loads for
sizing water supply systems. Accurate fixture unit values ensure that water supply piping is sized
appropriately for the building's demand.
9. When sizing a water supply branch pipe using the Hazen-Williams equation, which factor
represents the pipe's roughness?
A) C-factor
B) K-factor
C) F-factor
D) R-factor
Correct Answer: C-factor
Rationale: The C-factor (Hazen-Williams coefficient) quantifies pipe roughness; higher values
indicate smoother pipe material, resulting in less friction loss. New copper pipe commonly uses a
C-value of 150. The K-factor, F-factor, and R-factor are not used in the Hazen-Williams
equation for water supply sizing.
10. The Hazen-Williams coefficient (C) for new copper pipe used in water supply calculations is:
A) 100
B) 120
C) 130
D) 150
Correct Answer: 150
Rationale: New copper pipe commonly uses a C-value of 150 for Hazen-Williams calculations,
reflecting its relatively smooth interior surface. Lower C-values indicate rougher pipe and greater
friction loss. Using the correct C-value ensures accurate water supply sizing and pressure
calculations.
11. What is the minimum required size for a water service pipe from the street to the water
distribution system in a single-family dwelling, according to the Arkansas Plumbing Code?
