Texas Tradesman Plumber-Limited License
Practice Exam Questions And Correct
Answers (Verified Answers)
Page 1 of 59
,Question 1: According to the plumbing code applicable in Texas for a
Tradesman Plumber-Limited license holder, what is the minimum size of a
water service pipe serving a single-family dwelling with three bathrooms?
A. ½ inch
B. ¾ inch
C. 1 inch
D. 1¼ inch
CORRECT ANSWER: B. ¾ inch
Rationale: The minimum water service pipe size for a typical single-family residence
is ¾ inch to ensure adequate flow and pressure under peak demand conditions as
required by the adopted plumbing code.
Question 2: When installing a horizontal drain line for a water closet in a
residential application, what is the minimum slope required per foot of
horizontal run?
A. ⅛ inch per foot
B. ¼ inch per foot
C. ½ inch per foot
D. 1 inch per foot
CORRECT ANSWER: B. ¼ inch per foot
Rationale: Horizontal drainage piping 3 inches or larger requires a minimum slope
of ⅛ inch per foot, but standard practice and code for most residential drain lines,
including those serving water closets, mandate ¼ inch per foot to ensure proper
flow velocity and prevent solids deposition.
Question 3: A Tradesman Plumber-Limited is preparing to install a new gas
water heater. What is the minimum clearance required from the front of the
water heater to allow for servicing?
A. 6 inches
B. 12 inches
C. 18 inches
D. 24 inches
CORRECT ANSWER: D. 24 inches
Rationale: Manufacturer instructions and code requirements typically mandate a
minimum of 24 inches of clear working space in front of a water heater to permit
safe inspection, maintenance, and replacement of components.
Page 2 of 59
,Question 4: Which of the following materials is approved for use in a potable
water distribution system under the Texas plumbing code?
A. Cast iron soil pipe
B. Schedule 40 PVC
C. Type L copper tubing
D. Black steel pipe
CORRECT ANSWER: C. Type L copper tubing
Rationale: Type L copper tubing is specifically approved for potable water
distribution. Schedule 40 PVC is generally limited to drain, waste, and vent
applications, while black steel and cast iron are not approved for potable water.
Question 5: When roughing-in a lavatory, what is the standard height from the
finished floor to the center of the faucet holes on the lavatory?
A. 28 inches
B. 31 inches
C. 34 inches
D. 36 inches
CORRECT ANSWER: B. 31 inches
Rationale: The standard rough-in height for a lavatory faucet is approximately 31
inches above the finished floor to provide proper accessibility and ergonomic use
for the average adult.
Question 6: What is the minimum trap seal depth required for a floor drain
serving a residential garage?
A. 1 inch
B. 2 inches
C. 3 inches
D. 4 inches
CORRECT ANSWER: B. 2 inches
Rationale: The plumbing code requires a minimum trap seal of 2 inches for most
fixtures, including floor drains, to prevent the escape of sewer gases into the
building.
Question 7: A plumber is installing a new water closet. What is the minimum
clear space required in front of the water closet measured from the front of
the bowl?
A. 15 inches
B. 21 inches
Page 3 of 59
, C. 24 inches
D. 30 inches
CORRECT ANSWER: C. 24 inches
Rationale: Code requires a minimum of 24 inches of clear space in front of a water
closet to allow for proper use and accessibility.
Question 8: When connecting a dishwasher to the drainage system, what is the
required method to prevent backflow?
A. Direct connection to the soil stack
B. Air gap or high loop with a listed air gap fitting
C. Connection below the trap weir
D. Use of a check valve only
CORRECT ANSWER: B. Air gap or high loop with a listed air gap fitting
Rationale: An air gap or a properly installed high loop with an approved air gap
fitting is required to prevent contaminated water from siphoning back into the
dishwasher and potable water system.
Question 9: What is the maximum horizontal distance a vent may travel before
connecting to a vent stack or stack vent for a 2-inch fixture drain?
A. 5 feet
B. 8 feet
C. 10 feet
D. 20 feet
CORRECT ANSWER: B. 8 feet
Rationale: For a 2-inch fixture drain, the maximum developed length of the vent is
limited to prevent excessive pressure fluctuations; 8 feet is the typical maximum
horizontal distance allowed before the vent must rise vertically or connect to a
larger vent system.
Question 10: Which of the following is the correct minimum size for a building
sewer serving a single-family dwelling?
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
CORRECT ANSWER: C. 4 inches
Page 4 of 59
Practice Exam Questions And Correct
Answers (Verified Answers)
Page 1 of 59
,Question 1: According to the plumbing code applicable in Texas for a
Tradesman Plumber-Limited license holder, what is the minimum size of a
water service pipe serving a single-family dwelling with three bathrooms?
A. ½ inch
B. ¾ inch
C. 1 inch
D. 1¼ inch
CORRECT ANSWER: B. ¾ inch
Rationale: The minimum water service pipe size for a typical single-family residence
is ¾ inch to ensure adequate flow and pressure under peak demand conditions as
required by the adopted plumbing code.
Question 2: When installing a horizontal drain line for a water closet in a
residential application, what is the minimum slope required per foot of
horizontal run?
A. ⅛ inch per foot
B. ¼ inch per foot
C. ½ inch per foot
D. 1 inch per foot
CORRECT ANSWER: B. ¼ inch per foot
Rationale: Horizontal drainage piping 3 inches or larger requires a minimum slope
of ⅛ inch per foot, but standard practice and code for most residential drain lines,
including those serving water closets, mandate ¼ inch per foot to ensure proper
flow velocity and prevent solids deposition.
Question 3: A Tradesman Plumber-Limited is preparing to install a new gas
water heater. What is the minimum clearance required from the front of the
water heater to allow for servicing?
A. 6 inches
B. 12 inches
C. 18 inches
D. 24 inches
CORRECT ANSWER: D. 24 inches
Rationale: Manufacturer instructions and code requirements typically mandate a
minimum of 24 inches of clear working space in front of a water heater to permit
safe inspection, maintenance, and replacement of components.
Page 2 of 59
,Question 4: Which of the following materials is approved for use in a potable
water distribution system under the Texas plumbing code?
A. Cast iron soil pipe
B. Schedule 40 PVC
C. Type L copper tubing
D. Black steel pipe
CORRECT ANSWER: C. Type L copper tubing
Rationale: Type L copper tubing is specifically approved for potable water
distribution. Schedule 40 PVC is generally limited to drain, waste, and vent
applications, while black steel and cast iron are not approved for potable water.
Question 5: When roughing-in a lavatory, what is the standard height from the
finished floor to the center of the faucet holes on the lavatory?
A. 28 inches
B. 31 inches
C. 34 inches
D. 36 inches
CORRECT ANSWER: B. 31 inches
Rationale: The standard rough-in height for a lavatory faucet is approximately 31
inches above the finished floor to provide proper accessibility and ergonomic use
for the average adult.
Question 6: What is the minimum trap seal depth required for a floor drain
serving a residential garage?
A. 1 inch
B. 2 inches
C. 3 inches
D. 4 inches
CORRECT ANSWER: B. 2 inches
Rationale: The plumbing code requires a minimum trap seal of 2 inches for most
fixtures, including floor drains, to prevent the escape of sewer gases into the
building.
Question 7: A plumber is installing a new water closet. What is the minimum
clear space required in front of the water closet measured from the front of
the bowl?
A. 15 inches
B. 21 inches
Page 3 of 59
, C. 24 inches
D. 30 inches
CORRECT ANSWER: C. 24 inches
Rationale: Code requires a minimum of 24 inches of clear space in front of a water
closet to allow for proper use and accessibility.
Question 8: When connecting a dishwasher to the drainage system, what is the
required method to prevent backflow?
A. Direct connection to the soil stack
B. Air gap or high loop with a listed air gap fitting
C. Connection below the trap weir
D. Use of a check valve only
CORRECT ANSWER: B. Air gap or high loop with a listed air gap fitting
Rationale: An air gap or a properly installed high loop with an approved air gap
fitting is required to prevent contaminated water from siphoning back into the
dishwasher and potable water system.
Question 9: What is the maximum horizontal distance a vent may travel before
connecting to a vent stack or stack vent for a 2-inch fixture drain?
A. 5 feet
B. 8 feet
C. 10 feet
D. 20 feet
CORRECT ANSWER: B. 8 feet
Rationale: For a 2-inch fixture drain, the maximum developed length of the vent is
limited to prevent excessive pressure fluctuations; 8 feet is the typical maximum
horizontal distance allowed before the vent must rise vertically or connect to a
larger vent system.
Question 10: Which of the following is the correct minimum size for a building
sewer serving a single-family dwelling?
A. 2 inches
B. 3 inches
C. 4 inches
D. 6 inches
CORRECT ANSWER: C. 4 inches
Page 4 of 59
