TEXAS MASTER PLUMBER EXAM – 100 MOST TESTED
QUESTIONS WITH VERIFIED ANSWERS & RATIONALES |
LATEST 2026–2027 EDITION | INSTANT PDF DOWNLOAD
1. A licensed master plumber is overseeing the installation of a sanitary drainage system in a
new two-story commercial building. The plumbing inspector requires that the drainage and
vent piping be sized and installed per the Texas State Board of Plumbing Examiners rules.
Which of the following actions by the plumber would be most compliant with Texas plumbing
code requirements?
A. Install the drainage piping with a minimum slope of 1/4 inch per foot for pipes 3 inches and smaller, and
ensure all horizontal drainage lines are properly supported.
B. Use the International Plumbing Code without any Texas amendments since it is the adopted national
standard.
C. Install all drainage piping with a minimum slope of 1/8 inch per foot regardless of pipe size to save on labor
costs.
D. Design the system based on a fixture unit load calculation that exceeds the maximum allowable by the
code to allow for future expansion.
Answer: A. Install the drainage piping with a minimum slope of 1/4 inch per foot for pipes 3
inches and smaller, and ensure all horizontal drainage lines are properly supported.
2. During a rough-in inspection of a commercial building, the plumbing inspector notes that the
vent pipe for a bathroom group terminates through the roof less than 12 inches above the roof
surface. The plumber argues that the termination is acceptable because the roof has a 6:12
pitch. Which of the following is the correct code requirement for vent termination?
A. Vent pipes must extend at least 12 inches above the roof, measured from the upper side of the pipe, but
may be reduced to 6 inches if the roof is used for public assembly.
B. Vent pipes must terminate at least 12 inches above the roof, but if the roof is sloped more than 4:12, the
vent may be terminated at least 6 inches above the roof.
C. Vent pipes must terminate at least 12 inches above the roof, regardless of the roof pitch, unless in a snow
zone where they must be higher.
D. Vent pipes must terminate at least 24 inches above the roof to prevent snow blockage, regardless of
climate.
Answer: B. Vent pipes must terminate at least 12 inches above the roof, but if the roof is sloped
more than 4:12, the vent may be terminated at least 6 inches above the roof.
3. A master plumber is preparing to install a new water heater in a residential garage. The water
heater is a gas-fired, 50-gallon unit. According to the Texas plumbing code, which of the
following installation requirements is most critical?
A. The water heater must be installed on a metal stand so that the burner is at least 18 inches above the
garage floor.
B. The water heater must be anchored to the wall to prevent tipping during earthquakes, and the T&P valve
must be properly installed.
C. The water heater must be placed in a pan with a drain to protect the garage floor from water damage, and
the T&P valve must vent to the exterior.
D. The water heater must be elevated at least 12 inches above the floor to keep it away from potential
flooding.
Answer: B. The water heater must be anchored to the wall to prevent tipping during
,earthquakes, and the T&P valve must be properly installed.
4. A plumbing designer is tasked with sizing the water service pipe for a new apartment
building with 40 units, each with a bathroom group, kitchen sink, and clothes washer. The
building is served by a public water main with a static pressure of 50 psi. Using the fixture unit
method, the calculated demand is 400 water supply fixture units. What is the minimum required
water service pipe size based on the velocity limit of 8 ft/s?
A. 2 inches
B. 2-1/2 inches
C. 3 inches
D. 4 inches
Answer: C. 3 inches
5. In a multistory commercial building, the plumbing engineer must size the drainage stack for
a building with 20 flushometer valves on a single branch interval. Using the IPC fixture unit
values, each flushometer valve contributes 8 drainage fixture units. What is the minimum
required stack size if the stack offset is less than 45 degrees?
A. 3 inches
B. 4 inches
C. 5 inches
D. 6 inches
Answer: B. 4 inches
6. A master plumber is designing the venting system for a series of bathroom fixtures in a
commercial building. The plumbing inspector requires that the vents be sized based on the
total fixture units connected to the vent. Which of the following statements is true regarding the
sizing of a vent pipe?
A. The vent pipe diameter must be at least half the diameter of the drain pipe it serves, but never less than
1-1/4 inches.
B. The vent pipe diameter must be at least one-third the diameter of the drain pipe it serves, with a minimum
of 1-1/2 inches.
C. The vent pipe diameter must be equal to the diameter of the drain pipe it serves to ensure adequate air
flow.
D. The vent pipe diameter is determined solely by the length of the vent pipe, not the fixture units.
Answer: A. The vent pipe diameter must be at least half the diameter of the drain pipe it serves,
but never less than 1-1/4 inches.
7. During the plumbing rough-in of a new commercial kitchen, the inspector notices that the
floor drain is not provided with a trap primer. The plumber explains that the floor drain is not
subject to evaporation because it is rarely used. Which of the following is the correct
response?
A. The floor drain must have a trap primer because the trap seal can evaporate, allowing sewer gas to enter
the building.
B. The floor drain is exempt from trap primer requirements because it is not a code-required fixture.
C. The floor drain can be connected to a vent line to prevent evaporation, eliminating the need for a trap
primer.
D. The floor drain must be connected to a sanitary drainage system, but a trap primer is not required if the
drain is no more than 6 feet from a lavatory.
, Answer: A. The floor drain must have a trap primer because the trap seal can evaporate,
allowing sewer gas to enter the building.
8. A master plumber is laying out the drainage piping for a new bathroom group in a residential
home. The fixtures include a toilet, a shower, a double lavatory, and a bathtub. All fixtures are
on the same floor and will connect to a main horizontal branch. Which of the following is the
correct minimum size for the horizontal branch that will carry the combined drainage from all
these fixtures?
A. 3 inches
B. 4 inches
C. 2 inches
D. 2-1/2 inches
Answer: A. 3 inches
9. In a high-rise residential building, the plumbing designer must size the cold water supply
piping for the upper floors. The static pressure at the base of the building is 80 psi, and the
water pressure drops due to elevation. If the building is 200 feet tall, what is the static pressure
at the top floor, ignoring friction losses?
A. Approximately 8 psi
B. Approximately 20 psi
C. Approximately 40 psi
D. Approximately 60 psi
Answer: A. Approximately 8 psi
10. A master plumber is installing a domestic water supply system in a commercial building.
The system includes a backflow preventer on the main service line. Which type of backflow
preventer is required to protect a city water supply from a non-toxic substance, such as dye
from a testing kit?
A. Double check valve assembly
B. Reduced pressure zone (RPZ) assembly
C. Atmospheric vacuum breaker (AVB)
D. Pressure vacuum breaker (PVB)
Answer: A. Double check valve assembly
11. During a plumbing inspection, the inspector notices that a hose bibb is installed on the
exterior of a commercial building without any backflow prevention. The bibb is supplied from
the potable water system. Which of the following is the most appropriate action to correct this
violation?
A. Install a vacuum breaker on the hose bibb to prevent back-siphonage.
B. Replace the hose bibb with a self-draining type to prevent freezing.
C. Install a shut-off valve upstream of the hose bibb to isolate it.
D. Insulate the hose bibb to prevent it from freezing in cold weather.
Answer: A. Install a vacuum breaker on the hose bibb to prevent back-siphonage.
12. A master plumber is required to calculate the developed length of a vent pipe. The vent
connects to a fixture drain that is 4 feet long and has a total vent length of 25 feet. The pipe
diameter is 1-1/2 inches. Using the IPC vent sizing tables, what is the maximum number of
fixture units that can be served by this vent?
QUESTIONS WITH VERIFIED ANSWERS & RATIONALES |
LATEST 2026–2027 EDITION | INSTANT PDF DOWNLOAD
1. A licensed master plumber is overseeing the installation of a sanitary drainage system in a
new two-story commercial building. The plumbing inspector requires that the drainage and
vent piping be sized and installed per the Texas State Board of Plumbing Examiners rules.
Which of the following actions by the plumber would be most compliant with Texas plumbing
code requirements?
A. Install the drainage piping with a minimum slope of 1/4 inch per foot for pipes 3 inches and smaller, and
ensure all horizontal drainage lines are properly supported.
B. Use the International Plumbing Code without any Texas amendments since it is the adopted national
standard.
C. Install all drainage piping with a minimum slope of 1/8 inch per foot regardless of pipe size to save on labor
costs.
D. Design the system based on a fixture unit load calculation that exceeds the maximum allowable by the
code to allow for future expansion.
Answer: A. Install the drainage piping with a minimum slope of 1/4 inch per foot for pipes 3
inches and smaller, and ensure all horizontal drainage lines are properly supported.
2. During a rough-in inspection of a commercial building, the plumbing inspector notes that the
vent pipe for a bathroom group terminates through the roof less than 12 inches above the roof
surface. The plumber argues that the termination is acceptable because the roof has a 6:12
pitch. Which of the following is the correct code requirement for vent termination?
A. Vent pipes must extend at least 12 inches above the roof, measured from the upper side of the pipe, but
may be reduced to 6 inches if the roof is used for public assembly.
B. Vent pipes must terminate at least 12 inches above the roof, but if the roof is sloped more than 4:12, the
vent may be terminated at least 6 inches above the roof.
C. Vent pipes must terminate at least 12 inches above the roof, regardless of the roof pitch, unless in a snow
zone where they must be higher.
D. Vent pipes must terminate at least 24 inches above the roof to prevent snow blockage, regardless of
climate.
Answer: B. Vent pipes must terminate at least 12 inches above the roof, but if the roof is sloped
more than 4:12, the vent may be terminated at least 6 inches above the roof.
3. A master plumber is preparing to install a new water heater in a residential garage. The water
heater is a gas-fired, 50-gallon unit. According to the Texas plumbing code, which of the
following installation requirements is most critical?
A. The water heater must be installed on a metal stand so that the burner is at least 18 inches above the
garage floor.
B. The water heater must be anchored to the wall to prevent tipping during earthquakes, and the T&P valve
must be properly installed.
C. The water heater must be placed in a pan with a drain to protect the garage floor from water damage, and
the T&P valve must vent to the exterior.
D. The water heater must be elevated at least 12 inches above the floor to keep it away from potential
flooding.
Answer: B. The water heater must be anchored to the wall to prevent tipping during
,earthquakes, and the T&P valve must be properly installed.
4. A plumbing designer is tasked with sizing the water service pipe for a new apartment
building with 40 units, each with a bathroom group, kitchen sink, and clothes washer. The
building is served by a public water main with a static pressure of 50 psi. Using the fixture unit
method, the calculated demand is 400 water supply fixture units. What is the minimum required
water service pipe size based on the velocity limit of 8 ft/s?
A. 2 inches
B. 2-1/2 inches
C. 3 inches
D. 4 inches
Answer: C. 3 inches
5. In a multistory commercial building, the plumbing engineer must size the drainage stack for
a building with 20 flushometer valves on a single branch interval. Using the IPC fixture unit
values, each flushometer valve contributes 8 drainage fixture units. What is the minimum
required stack size if the stack offset is less than 45 degrees?
A. 3 inches
B. 4 inches
C. 5 inches
D. 6 inches
Answer: B. 4 inches
6. A master plumber is designing the venting system for a series of bathroom fixtures in a
commercial building. The plumbing inspector requires that the vents be sized based on the
total fixture units connected to the vent. Which of the following statements is true regarding the
sizing of a vent pipe?
A. The vent pipe diameter must be at least half the diameter of the drain pipe it serves, but never less than
1-1/4 inches.
B. The vent pipe diameter must be at least one-third the diameter of the drain pipe it serves, with a minimum
of 1-1/2 inches.
C. The vent pipe diameter must be equal to the diameter of the drain pipe it serves to ensure adequate air
flow.
D. The vent pipe diameter is determined solely by the length of the vent pipe, not the fixture units.
Answer: A. The vent pipe diameter must be at least half the diameter of the drain pipe it serves,
but never less than 1-1/4 inches.
7. During the plumbing rough-in of a new commercial kitchen, the inspector notices that the
floor drain is not provided with a trap primer. The plumber explains that the floor drain is not
subject to evaporation because it is rarely used. Which of the following is the correct
response?
A. The floor drain must have a trap primer because the trap seal can evaporate, allowing sewer gas to enter
the building.
B. The floor drain is exempt from trap primer requirements because it is not a code-required fixture.
C. The floor drain can be connected to a vent line to prevent evaporation, eliminating the need for a trap
primer.
D. The floor drain must be connected to a sanitary drainage system, but a trap primer is not required if the
drain is no more than 6 feet from a lavatory.
, Answer: A. The floor drain must have a trap primer because the trap seal can evaporate,
allowing sewer gas to enter the building.
8. A master plumber is laying out the drainage piping for a new bathroom group in a residential
home. The fixtures include a toilet, a shower, a double lavatory, and a bathtub. All fixtures are
on the same floor and will connect to a main horizontal branch. Which of the following is the
correct minimum size for the horizontal branch that will carry the combined drainage from all
these fixtures?
A. 3 inches
B. 4 inches
C. 2 inches
D. 2-1/2 inches
Answer: A. 3 inches
9. In a high-rise residential building, the plumbing designer must size the cold water supply
piping for the upper floors. The static pressure at the base of the building is 80 psi, and the
water pressure drops due to elevation. If the building is 200 feet tall, what is the static pressure
at the top floor, ignoring friction losses?
A. Approximately 8 psi
B. Approximately 20 psi
C. Approximately 40 psi
D. Approximately 60 psi
Answer: A. Approximately 8 psi
10. A master plumber is installing a domestic water supply system in a commercial building.
The system includes a backflow preventer on the main service line. Which type of backflow
preventer is required to protect a city water supply from a non-toxic substance, such as dye
from a testing kit?
A. Double check valve assembly
B. Reduced pressure zone (RPZ) assembly
C. Atmospheric vacuum breaker (AVB)
D. Pressure vacuum breaker (PVB)
Answer: A. Double check valve assembly
11. During a plumbing inspection, the inspector notices that a hose bibb is installed on the
exterior of a commercial building without any backflow prevention. The bibb is supplied from
the potable water system. Which of the following is the most appropriate action to correct this
violation?
A. Install a vacuum breaker on the hose bibb to prevent back-siphonage.
B. Replace the hose bibb with a self-draining type to prevent freezing.
C. Install a shut-off valve upstream of the hose bibb to isolate it.
D. Insulate the hose bibb to prevent it from freezing in cold weather.
Answer: A. Install a vacuum breaker on the hose bibb to prevent back-siphonage.
12. A master plumber is required to calculate the developed length of a vent pipe. The vent
connects to a fixture drain that is 4 feet long and has a total vent length of 25 feet. The pipe
diameter is 1-1/2 inches. Using the IPC vent sizing tables, what is the maximum number of
fixture units that can be served by this vent?
