Texas Tradesman Plumber-Limited License EXAM
with Questions and Answers/Plus a Rationale Updated
2026 A+/Instant Download PDF
EXAM COVERAGE - 1. Plumbing Codes and Administrative
Regulations - 2. Sanitary Drainage, Waste, and Vent Systems - 3.
Water Supply and Distribution Systems - 4. Plumbing Fixtures,
Faucets, and Fixture Fittings - 5. Water Heaters and Safety Controls -
6. Safety Standards and Practical Installation
1. A plumber is installing a 3-inch horizontal sanitary drainage pipe in a commercial building and
must establish the correct minimum slope to ensure self-cleansing velocity. According to
standard plumbing code requirements, what is the mandatory minimum slope for this pipe?
A. 1/16 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
CORRECT ANSWER : B
Rationale: Horizontal drainage piping sizing 3 inches and smaller requires a minimum slope of
1/4 inch per foot to maintain adequate fluid velocity and prevent solid accumulation. Options A
provides insufficient velocity, while options C and D create excessive drop that can cause liquid
to run away from solid waste.
2. When installing a temperature and pressure (T&P) relief valve discharge pipe on a residential
water heater, which of the following material specifications is strictly prohibited by code?
A. CPVC rigid plastic tubing
B. Threaded PVC plastic pipe
C. Galvanized steel piping
D. Type L copper tubing
CORRECT ANSWER : B
, Rationale: PVC plastic pipe is not rated for the high temperatures associated with T&P relief
valve discharge and is prohibited by code for this application. CPVC, copper, and galvanized
steel possess thermal ratings capable of withstanding emergency temperature spikes safely.
3. An inspector notes that a building sewer and a water service pipe are being laid in the same
trench. Under standard plumbing code provisions, what is the minimum horizontal separation
required between the water service pipe and the building sewer unless specific elevation
exceptions are met?
A. 12 inches
B. 24 inches
C. 60 inches
D. 120 inches
CORRECT ANSWER : C
Rationale: Standard code mandates a minimum horizontal separation of 60 inches (5 feet)
between a water service pipe and a building sewer to prevent cross-contamination in the event of
sewer pipe failure or joint leakage. Lesser distances like 12 or 24 inches fail to provide an
adequate safety buffer.
4. A residential kitchen sink discharges into a drainage network. What is the maximum vertical
distance permitted by code between the fixture outlet and the trap weir?
A. 12 inches
B. 24 inches
C. 30 inches
D. 36 inches
CORRECT ANSWER : B
Rationale: The vertical distance from the fixture outlet to the trap weir must not exceed 24 inches
to prevent excessive unventilated pipe exposure that can harbor slime and organic buildup.
Distances greater than 24 inches compromise trap seal integrity and create un-trapped spaces.
5. When performing a pneumatic (air) test on a newly installed DWV system, what is the standard
minimum test pressure that must be applied and held for a specified duration?
A. 1.0 psi
, B. 5.0 psi
C. 15.0 psi
D. 50.0 psi
CORRECT ANSWER : B
Rationale: A pneumatic test for DWV systems requires a constant pressure of 5.0 psi applied and
held without reduction for a minimum period of 15 minutes. Lower pressures will not reveal
micro-leaks, whereas higher pressures risk structural failure of plastic pipe components.
6. Which of the following backflow prevention assemblies provides the highest level of protection
and is required by code for continuous pressure health-hazard cross-connections?
A. Dual check valve device
B. Atmospheric vacuum breaker
C. Reduced pressure principle backflow preventer
D. Pressure vacuum breaker assembly
CORRECT ANSWER : C
Rationale: The reduced pressure principle (RP) backflow preventer incorporates an
automatically operated differential relief valve, making it the only mechanical assembly
approved for high-hazard, continuous pressure applications. Atmospheric vacuum breakers
cannot withstand backpressure or be installed under continuous pressure.
7. A plumber needs to join two lengths of cast iron soil pipe using a compression-joint hubless
coupling with a stainless steel shield and neoprene gasket. What tool is explicitly required to
verify proper installation torque on the clamping bands?
A. Adjustable slip-joint pliers
B. Open-end wrench
C. Calibrated torque wrench
D. Impact driver without clutch settings
CORRECT ANSWER : C
Rationale: Manufacturers and plumbing codes mandate the use of a calibrated torque wrench to
ensure the stainless steel bands are tightened to exact manufacturer specifications (typically 60
, inch-pounds). Standard hand tools or uncalibrated impact drivers risk under-tightening or
shearing the band clamp.
8. In a multi-story building drainage layout, what is the primary structural and hydraulic function of
a building relief vent?
A. To supply combustion air to water heating equipment
B. To provide a connection path between the drainage stack and vent stack to equalize
pressure differentials
C. To serve as a cleanout access point for clearing heavy blockages
D. To catch grease discharge prior to entering the municipal main
CORRECT ANSWER : B
Rationale: A building relief vent connects the horizontal drainage branch or building drain to
the vent system to mitigate pressure fluctuations caused by high-volume slug flow from upper
stories. It ensures smooth air circulation throughout the vertical stack network.
9. When sizing a building water supply distribution system, what critical hydraulic factor dictates
the minimum size of the service entrance pipe?
A. Total linear footage of waste piping
B. Total water supply fixture units (WSFU) and available water pressure
C. Ambient ground temperature surrounding the meter box
D. Number of stories in the adjacent structure
CORRECT ANSWER : B
Rationale: Water supply distribution piping is sized based on Water Supply Fixture Units
(WSFU) to estimate peak demand coupled with incoming service pressure and flow velocity
limitations. Drainage footage and ambient temperatures do not dictate supply pipe diameter.
10. A continuous waste and vent system is utilized for a battery of three commercial lavatories. What
is the maximum number of fixtures permitted on a single horizontal branch drain before an
individual vent is required?
A. 1 fixture
B. 2 fixtures
with Questions and Answers/Plus a Rationale Updated
2026 A+/Instant Download PDF
EXAM COVERAGE - 1. Plumbing Codes and Administrative
Regulations - 2. Sanitary Drainage, Waste, and Vent Systems - 3.
Water Supply and Distribution Systems - 4. Plumbing Fixtures,
Faucets, and Fixture Fittings - 5. Water Heaters and Safety Controls -
6. Safety Standards and Practical Installation
1. A plumber is installing a 3-inch horizontal sanitary drainage pipe in a commercial building and
must establish the correct minimum slope to ensure self-cleansing velocity. According to
standard plumbing code requirements, what is the mandatory minimum slope for this pipe?
A. 1/16 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
CORRECT ANSWER : B
Rationale: Horizontal drainage piping sizing 3 inches and smaller requires a minimum slope of
1/4 inch per foot to maintain adequate fluid velocity and prevent solid accumulation. Options A
provides insufficient velocity, while options C and D create excessive drop that can cause liquid
to run away from solid waste.
2. When installing a temperature and pressure (T&P) relief valve discharge pipe on a residential
water heater, which of the following material specifications is strictly prohibited by code?
A. CPVC rigid plastic tubing
B. Threaded PVC plastic pipe
C. Galvanized steel piping
D. Type L copper tubing
CORRECT ANSWER : B
, Rationale: PVC plastic pipe is not rated for the high temperatures associated with T&P relief
valve discharge and is prohibited by code for this application. CPVC, copper, and galvanized
steel possess thermal ratings capable of withstanding emergency temperature spikes safely.
3. An inspector notes that a building sewer and a water service pipe are being laid in the same
trench. Under standard plumbing code provisions, what is the minimum horizontal separation
required between the water service pipe and the building sewer unless specific elevation
exceptions are met?
A. 12 inches
B. 24 inches
C. 60 inches
D. 120 inches
CORRECT ANSWER : C
Rationale: Standard code mandates a minimum horizontal separation of 60 inches (5 feet)
between a water service pipe and a building sewer to prevent cross-contamination in the event of
sewer pipe failure or joint leakage. Lesser distances like 12 or 24 inches fail to provide an
adequate safety buffer.
4. A residential kitchen sink discharges into a drainage network. What is the maximum vertical
distance permitted by code between the fixture outlet and the trap weir?
A. 12 inches
B. 24 inches
C. 30 inches
D. 36 inches
CORRECT ANSWER : B
Rationale: The vertical distance from the fixture outlet to the trap weir must not exceed 24 inches
to prevent excessive unventilated pipe exposure that can harbor slime and organic buildup.
Distances greater than 24 inches compromise trap seal integrity and create un-trapped spaces.
5. When performing a pneumatic (air) test on a newly installed DWV system, what is the standard
minimum test pressure that must be applied and held for a specified duration?
A. 1.0 psi
, B. 5.0 psi
C. 15.0 psi
D. 50.0 psi
CORRECT ANSWER : B
Rationale: A pneumatic test for DWV systems requires a constant pressure of 5.0 psi applied and
held without reduction for a minimum period of 15 minutes. Lower pressures will not reveal
micro-leaks, whereas higher pressures risk structural failure of plastic pipe components.
6. Which of the following backflow prevention assemblies provides the highest level of protection
and is required by code for continuous pressure health-hazard cross-connections?
A. Dual check valve device
B. Atmospheric vacuum breaker
C. Reduced pressure principle backflow preventer
D. Pressure vacuum breaker assembly
CORRECT ANSWER : C
Rationale: The reduced pressure principle (RP) backflow preventer incorporates an
automatically operated differential relief valve, making it the only mechanical assembly
approved for high-hazard, continuous pressure applications. Atmospheric vacuum breakers
cannot withstand backpressure or be installed under continuous pressure.
7. A plumber needs to join two lengths of cast iron soil pipe using a compression-joint hubless
coupling with a stainless steel shield and neoprene gasket. What tool is explicitly required to
verify proper installation torque on the clamping bands?
A. Adjustable slip-joint pliers
B. Open-end wrench
C. Calibrated torque wrench
D. Impact driver without clutch settings
CORRECT ANSWER : C
Rationale: Manufacturers and plumbing codes mandate the use of a calibrated torque wrench to
ensure the stainless steel bands are tightened to exact manufacturer specifications (typically 60
, inch-pounds). Standard hand tools or uncalibrated impact drivers risk under-tightening or
shearing the band clamp.
8. In a multi-story building drainage layout, what is the primary structural and hydraulic function of
a building relief vent?
A. To supply combustion air to water heating equipment
B. To provide a connection path between the drainage stack and vent stack to equalize
pressure differentials
C. To serve as a cleanout access point for clearing heavy blockages
D. To catch grease discharge prior to entering the municipal main
CORRECT ANSWER : B
Rationale: A building relief vent connects the horizontal drainage branch or building drain to
the vent system to mitigate pressure fluctuations caused by high-volume slug flow from upper
stories. It ensures smooth air circulation throughout the vertical stack network.
9. When sizing a building water supply distribution system, what critical hydraulic factor dictates
the minimum size of the service entrance pipe?
A. Total linear footage of waste piping
B. Total water supply fixture units (WSFU) and available water pressure
C. Ambient ground temperature surrounding the meter box
D. Number of stories in the adjacent structure
CORRECT ANSWER : B
Rationale: Water supply distribution piping is sized based on Water Supply Fixture Units
(WSFU) to estimate peak demand coupled with incoming service pressure and flow velocity
limitations. Drainage footage and ambient temperatures do not dictate supply pipe diameter.
10. A continuous waste and vent system is utilized for a battery of three commercial lavatories. What
is the maximum number of fixtures permitted on a single horizontal branch drain before an
individual vent is required?
A. 1 fixture
B. 2 fixtures
