Kentucky Master Plumber / Journeyman
Plumber Examination Practice Questions
And Correct A
1. A 4-inch building drain with a slope of 1/8 inch per foot receives a total of 1,200
fixture units. According to the Kentucky Plumbing Code, what is the minimum
required size for the building drain if the slope cannot be increased?
A. 4 inches
B. 5 inches
C. 6 inches
D. 8 inches
Answer: C. 6 inches
Rationale: At 1/8 inch per foot slope, a 4-inch drain can handle only 1,000 fixture units;
1,200 fixture units require a 6-inch drain. A 5-inch drain is not a standard size and would
still be insufficient. Therefore, C is correct.
2. In a 12-story building, a 6-inch vertical stack serves 10 branch intervals. What is the
minimum required size of the vent stack if the building drain is 8 inches and the stack
receives 500 fixture units?
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
Answer: B. 3 inches
Rationale: Per Kentucky Plumbing Code, a vent stack for a 6-inch stack with 10 branch
intervals must be at least half the diameter of the soil stack, but not less than 3 inches.
Thus, 3 inches is the minimum. A 2-inch vent is too small; 4-inch and 6-inch are oversized
and unnecessary.
Page 1 of 71
,3. A water service line is installed in a area where the winter design temperature is
10°F. The pipe material is PEX. What is the minimum required burial depth to
prevent freezing, assuming no insulation?
A. 12 inches
B. 18 inches
C. 24 inches
D. 36 inches
Answer: C. 24 inches
Rationale: Kentucky Plumbing Code requires water service lines to be buried at least 24
inches below finished grade in areas with freezing temperatures. PEX has some freeze
resistance but still requires this depth. 12 or 18 inches are insufficient; 36 inches is
excessive for this climate.
4. A reduced pressure zone (RPZ) backflow preventer is installed on a fire sprinkler
system. During annual testing, the relief valve discharges continuously. Which of the
following is the most likely cause?
A. Fouled first check valve
B. Fouled second check valve
C. Debris on the relief valve seat
D. Low supply pressure
Answer: B. Fouled second check valve
Rationale: Continuous discharge from the relief valve indicates that the second check valve
is not holding, allowing pressure to build in the zone between checks and forcing the relief
valve to open. A fouled first check would cause the relief valve to discharge only during
backflow conditions, not continuously. Debris on the relief valve seat would cause leakage
but not continuous discharge. Low supply pressure would not cause continuous discharge.
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,5. When sizing a gas piping system for a residential installation, the total equivalent
length of the longest run is 150 feet. The gas is natural gas with a heating value of
1,000 BTU/ft³ and a specific gravity of 0.60. The total demand is 200,000 BTU/hr.
Using the longest run method, what is the minimum nominal pipe size required for the
main line?
A. 1/2 inch
B. 3/4 inch
C. 1 inch
D. 1-1/4 inch
Answer: C. 1 inch
Rationale: According to NFPA 54 and Kentucky modifications, for a 150-foot run with
200,000 BTU/hr demand, a 1-inch pipe is required. A 3/4-inch pipe would only handle
about 150,000 BTU/hr at that length. 1-1/4 inch is oversized but acceptable; however, the
minimum required is 1 inch.
6. A plumbing system uses a combination waste and vent. Which of the following is a
critical requirement for this system?
A. The horizontal branch must have a minimum slope of 1/4 inch per foot.
B. The developed length of the horizontal branch must not exceed 15 feet.
C. The vertical drop from the fixture outlet to the horizontal branch must not exceed 2
feet.
D. The horizontal branch must connect to a vertical stack at least 2 inches in diameter.
Answer: B. The developed length of the horizontal branch must not exceed 15 feet.
Rationale: For a combination waste and vent system, the developed length of the horizontal
branch is limited to 15 feet to ensure proper drainage and venting. Slope must be at least
1/8 inch per foot, not 1/4. The vertical drop limitation is 1 foot, not 2. Connection to a stack
is not the critical factor; the length limit is key.
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, 7. A water heater is installed in a seismic zone. The Kentucky Plumbing Code requires
strapping. Which of the following best describes the required strapping configuration?
A. One strap at the top third and one at the bottom third.
B. Two straps within the top and bottom 12 inches of the tank.
C. One strap at the middle and one at the bottom.
D. Two straps within the top and bottom 24 inches of the tank.
Answer: B. Two straps within the top and bottom 12 inches of the tank.
Rationale: Kentucky Plumbing Code requires water heaters to be strapped with two straps,
one within the top 12 inches and one within the bottom 12 inches of the tank. This prevents
tipping during seismic activity. Other configurations do not meet code.
8. A grease interceptor is required for a commercial kitchen. The interceptor is rated
at 50 GPM. What is the minimum required capacity in gallons for the interceptor if it
serves a sink with a 2-inch drain?
A. 50 gallons
B. 100 gallons
C. 150 gallons
D. 200 gallons
Answer: B. 100 gallons
Rationale: The Kentucky Plumbing Code requires grease interceptors to have a capacity of
at least twice the flow rate in GPM. For a 50 GPM interceptor, the minimum capacity is
100 gallons. 50 gallons is insufficient; 150 and 200 exceed the minimum but are not
required.
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Plumber Examination Practice Questions
And Correct A
1. A 4-inch building drain with a slope of 1/8 inch per foot receives a total of 1,200
fixture units. According to the Kentucky Plumbing Code, what is the minimum
required size for the building drain if the slope cannot be increased?
A. 4 inches
B. 5 inches
C. 6 inches
D. 8 inches
Answer: C. 6 inches
Rationale: At 1/8 inch per foot slope, a 4-inch drain can handle only 1,000 fixture units;
1,200 fixture units require a 6-inch drain. A 5-inch drain is not a standard size and would
still be insufficient. Therefore, C is correct.
2. In a 12-story building, a 6-inch vertical stack serves 10 branch intervals. What is the
minimum required size of the vent stack if the building drain is 8 inches and the stack
receives 500 fixture units?
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
Answer: B. 3 inches
Rationale: Per Kentucky Plumbing Code, a vent stack for a 6-inch stack with 10 branch
intervals must be at least half the diameter of the soil stack, but not less than 3 inches.
Thus, 3 inches is the minimum. A 2-inch vent is too small; 4-inch and 6-inch are oversized
and unnecessary.
Page 1 of 71
,3. A water service line is installed in a area where the winter design temperature is
10°F. The pipe material is PEX. What is the minimum required burial depth to
prevent freezing, assuming no insulation?
A. 12 inches
B. 18 inches
C. 24 inches
D. 36 inches
Answer: C. 24 inches
Rationale: Kentucky Plumbing Code requires water service lines to be buried at least 24
inches below finished grade in areas with freezing temperatures. PEX has some freeze
resistance but still requires this depth. 12 or 18 inches are insufficient; 36 inches is
excessive for this climate.
4. A reduced pressure zone (RPZ) backflow preventer is installed on a fire sprinkler
system. During annual testing, the relief valve discharges continuously. Which of the
following is the most likely cause?
A. Fouled first check valve
B. Fouled second check valve
C. Debris on the relief valve seat
D. Low supply pressure
Answer: B. Fouled second check valve
Rationale: Continuous discharge from the relief valve indicates that the second check valve
is not holding, allowing pressure to build in the zone between checks and forcing the relief
valve to open. A fouled first check would cause the relief valve to discharge only during
backflow conditions, not continuously. Debris on the relief valve seat would cause leakage
but not continuous discharge. Low supply pressure would not cause continuous discharge.
Page 2 of 71
,5. When sizing a gas piping system for a residential installation, the total equivalent
length of the longest run is 150 feet. The gas is natural gas with a heating value of
1,000 BTU/ft³ and a specific gravity of 0.60. The total demand is 200,000 BTU/hr.
Using the longest run method, what is the minimum nominal pipe size required for the
main line?
A. 1/2 inch
B. 3/4 inch
C. 1 inch
D. 1-1/4 inch
Answer: C. 1 inch
Rationale: According to NFPA 54 and Kentucky modifications, for a 150-foot run with
200,000 BTU/hr demand, a 1-inch pipe is required. A 3/4-inch pipe would only handle
about 150,000 BTU/hr at that length. 1-1/4 inch is oversized but acceptable; however, the
minimum required is 1 inch.
6. A plumbing system uses a combination waste and vent. Which of the following is a
critical requirement for this system?
A. The horizontal branch must have a minimum slope of 1/4 inch per foot.
B. The developed length of the horizontal branch must not exceed 15 feet.
C. The vertical drop from the fixture outlet to the horizontal branch must not exceed 2
feet.
D. The horizontal branch must connect to a vertical stack at least 2 inches in diameter.
Answer: B. The developed length of the horizontal branch must not exceed 15 feet.
Rationale: For a combination waste and vent system, the developed length of the horizontal
branch is limited to 15 feet to ensure proper drainage and venting. Slope must be at least
1/8 inch per foot, not 1/4. The vertical drop limitation is 1 foot, not 2. Connection to a stack
is not the critical factor; the length limit is key.
Page 3 of 71
, 7. A water heater is installed in a seismic zone. The Kentucky Plumbing Code requires
strapping. Which of the following best describes the required strapping configuration?
A. One strap at the top third and one at the bottom third.
B. Two straps within the top and bottom 12 inches of the tank.
C. One strap at the middle and one at the bottom.
D. Two straps within the top and bottom 24 inches of the tank.
Answer: B. Two straps within the top and bottom 12 inches of the tank.
Rationale: Kentucky Plumbing Code requires water heaters to be strapped with two straps,
one within the top 12 inches and one within the bottom 12 inches of the tank. This prevents
tipping during seismic activity. Other configurations do not meet code.
8. A grease interceptor is required for a commercial kitchen. The interceptor is rated
at 50 GPM. What is the minimum required capacity in gallons for the interceptor if it
serves a sink with a 2-inch drain?
A. 50 gallons
B. 100 gallons
C. 150 gallons
D. 200 gallons
Answer: B. 100 gallons
Rationale: The Kentucky Plumbing Code requires grease interceptors to have a capacity of
at least twice the flow rate in GPM. For a 50 GPM interceptor, the minimum capacity is
100 gallons. 50 gallons is insufficient; 150 and 200 exceed the minimum but are not
required.
Page 4 of 71
