Arkansas Master Plumber Exam Newest
Update Version Questions & Detailed
Correct Answers
Question 1
The temperature of water from tankless water heaters shall be a maximum of how
many degrees Fahrenheit when intended for domestic use?
Correct Answer
140 degrees (501.6)
Question 2
A water closet, urinal, or lavatory shall not be closer than how many inches from its
center to any side wall?
Correct Answer
15 inches (405.3.1)
Question 3
Storm drain
Correct Answer
Piping within a public or private premise that conveys rainwater, surface water,
subsurface water and similar liquid wastes to a point of disposal. (Pg 9)
Question 4
What is a fixture drain?
Correct Answer
The drain from the trap of a fixture to a junction with any other drain pipe. (Pg 10)
Page 1 of 153
,Question 5
Meter boxes shall be constructed in such a manner that prevents what from entering
a structure by way of the water service pipes?
Correct Answer
Rodents (304.3)
Question 1: What is the minimum required horizontal slope for a 2-inch diameter
drainage pipe under standard plumbing codes?
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: B. 1/4 inch per foot
Rationale: Standard model codes and plumbing rules require a minimum slope of
1/4 inch per foot for drainage piping 2 inches in diameter to ensure proper self-
cleansing velocity and prevent solid accumulation.
Question 2: Which type of vent extends through the roof of a structure to maintain
atmospheric pressure balance and prevent trap siphoning?
A. Relief vent
B. Circuit vent
C. Stack vent
D. Air admittance valve
CORRECT ANSWER: C. Stack vent
Rationale: A stack vent is an extension of a soil or waste stack above the highest
horizontal fixture branch, terminating outdoors to release sewer gases and protect
trap seals from back pressure or siphoning.
Question 3: Which of the following piping materials is generally prohibited by
plumbing regulations for domestic potable water supply distribution lines?
A. Type L Copper
B. Cross-linked Polyethylene (PEX)
Page 2 of 153
,C. PVC Schedule 40
D. Chlorinated Polyvinyl Chloride (CPVC)
CORRECT ANSWER: C. PVC Schedule 40
Rationale: PVC Schedule 40 is approved for drainage, waste, and vent (DWV) or
cold-water exterior underground applications, but it is not rated or approved for
hot and cold interior potable water supply lines due to temperature limitations.
Question 4: What is the maximum allowable horizontal distance from a water closet
trap to its vent fitting?
A. 2 feet
B. 3 feet
C. 5 feet
D. 6 feet
CORRECT ANSWER: D. 6 feet
Rationale: Model codes restrict the maximum distance between a fixture trap and its
vent to prevent excessive pressure differentials that could siphon the trap seal,
establishing 6 feet as a common limit depending on pipe size.
Question 5: Which type of valve is typically mandated or preferred for isolating a
water heater to ensure positive shut-off and minimum flow restriction?
A. Gate valve
B. Ball valve
C. Globe valve
D. Check valve
CORRECT ANSWER: B. Ball valve
Rationale: Ball valves provide a reliable, quarter-turn, full-port tight seal with
minimal pressure drop, making them the industry standard for isolating water
heaters and major plumbing fixtures.
Question 6: What is the standard minimum burial depth for water service piping to
protect against freezing conditions in moderate climate zones like Arkansas?
A. 6 inches
Page 3 of 153
, B. 12 inches
C. 18 inches
D. 36 inches
CORRECT ANSWER: C. 18 inches
Rationale: Water service piping must be installed below the local frost line to
prevent freezing, with 18 inches being a common benchmark standard specified in
regional plumbing codes for many areas.
Question 7: What is the primary function of installing a dielectric union when joining
copper water tubing to galvanized steel piping?
A. Increase overall system water pressure
B. Prevent galvanic corrosion caused by dissimilar metals
C. Filter out mineral sediments and debris
D. Provide a flexible joint for thermal expansion
CORRECT ANSWER: B. Prevent galvanic corrosion caused by dissimilar metals
Rationale: Dielectric unions use an insulating gasket and sleeve to physically
separate dissimilar metals (like copper and steel), preventing destructive galvanic
corrosion caused by electrical current exchange.
Question 8: What is the minimum required air gap distance above the flood level rim
of a plumbing fixture to prevent backflow contamination?
A. Equal to twice the effective opening diameter
B. At least 1 inch or twice the diameter of the supply inlet
C. Exactly 6 inches regardless of pipe size
D. 1/2 inch minimum
CORRECT ANSWER: B. At least 1 inch or twice the diameter of the supply inlet
Rationale: An air gap must be at least twice the diameter of the effective supply
opening, and never less than 1 inch, to ensure a physical break preventing
backsiphonage of contaminated water into potable lines.
Question 9: Which device is required on a closed domestic water heating system to
protect against dangerous pressure build-up caused by thermal expansion?
Page 4 of 153
Update Version Questions & Detailed
Correct Answers
Question 1
The temperature of water from tankless water heaters shall be a maximum of how
many degrees Fahrenheit when intended for domestic use?
Correct Answer
140 degrees (501.6)
Question 2
A water closet, urinal, or lavatory shall not be closer than how many inches from its
center to any side wall?
Correct Answer
15 inches (405.3.1)
Question 3
Storm drain
Correct Answer
Piping within a public or private premise that conveys rainwater, surface water,
subsurface water and similar liquid wastes to a point of disposal. (Pg 9)
Question 4
What is a fixture drain?
Correct Answer
The drain from the trap of a fixture to a junction with any other drain pipe. (Pg 10)
Page 1 of 153
,Question 5
Meter boxes shall be constructed in such a manner that prevents what from entering
a structure by way of the water service pipes?
Correct Answer
Rodents (304.3)
Question 1: What is the minimum required horizontal slope for a 2-inch diameter
drainage pipe under standard plumbing codes?
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: B. 1/4 inch per foot
Rationale: Standard model codes and plumbing rules require a minimum slope of
1/4 inch per foot for drainage piping 2 inches in diameter to ensure proper self-
cleansing velocity and prevent solid accumulation.
Question 2: Which type of vent extends through the roof of a structure to maintain
atmospheric pressure balance and prevent trap siphoning?
A. Relief vent
B. Circuit vent
C. Stack vent
D. Air admittance valve
CORRECT ANSWER: C. Stack vent
Rationale: A stack vent is an extension of a soil or waste stack above the highest
horizontal fixture branch, terminating outdoors to release sewer gases and protect
trap seals from back pressure or siphoning.
Question 3: Which of the following piping materials is generally prohibited by
plumbing regulations for domestic potable water supply distribution lines?
A. Type L Copper
B. Cross-linked Polyethylene (PEX)
Page 2 of 153
,C. PVC Schedule 40
D. Chlorinated Polyvinyl Chloride (CPVC)
CORRECT ANSWER: C. PVC Schedule 40
Rationale: PVC Schedule 40 is approved for drainage, waste, and vent (DWV) or
cold-water exterior underground applications, but it is not rated or approved for
hot and cold interior potable water supply lines due to temperature limitations.
Question 4: What is the maximum allowable horizontal distance from a water closet
trap to its vent fitting?
A. 2 feet
B. 3 feet
C. 5 feet
D. 6 feet
CORRECT ANSWER: D. 6 feet
Rationale: Model codes restrict the maximum distance between a fixture trap and its
vent to prevent excessive pressure differentials that could siphon the trap seal,
establishing 6 feet as a common limit depending on pipe size.
Question 5: Which type of valve is typically mandated or preferred for isolating a
water heater to ensure positive shut-off and minimum flow restriction?
A. Gate valve
B. Ball valve
C. Globe valve
D. Check valve
CORRECT ANSWER: B. Ball valve
Rationale: Ball valves provide a reliable, quarter-turn, full-port tight seal with
minimal pressure drop, making them the industry standard for isolating water
heaters and major plumbing fixtures.
Question 6: What is the standard minimum burial depth for water service piping to
protect against freezing conditions in moderate climate zones like Arkansas?
A. 6 inches
Page 3 of 153
, B. 12 inches
C. 18 inches
D. 36 inches
CORRECT ANSWER: C. 18 inches
Rationale: Water service piping must be installed below the local frost line to
prevent freezing, with 18 inches being a common benchmark standard specified in
regional plumbing codes for many areas.
Question 7: What is the primary function of installing a dielectric union when joining
copper water tubing to galvanized steel piping?
A. Increase overall system water pressure
B. Prevent galvanic corrosion caused by dissimilar metals
C. Filter out mineral sediments and debris
D. Provide a flexible joint for thermal expansion
CORRECT ANSWER: B. Prevent galvanic corrosion caused by dissimilar metals
Rationale: Dielectric unions use an insulating gasket and sleeve to physically
separate dissimilar metals (like copper and steel), preventing destructive galvanic
corrosion caused by electrical current exchange.
Question 8: What is the minimum required air gap distance above the flood level rim
of a plumbing fixture to prevent backflow contamination?
A. Equal to twice the effective opening diameter
B. At least 1 inch or twice the diameter of the supply inlet
C. Exactly 6 inches regardless of pipe size
D. 1/2 inch minimum
CORRECT ANSWER: B. At least 1 inch or twice the diameter of the supply inlet
Rationale: An air gap must be at least twice the diameter of the effective supply
opening, and never less than 1 inch, to ensure a physical break preventing
backsiphonage of contaminated water into potable lines.
Question 9: Which device is required on a closed domestic water heating system to
protect against dangerous pressure build-up caused by thermal expansion?
Page 4 of 153
