Texas Master Plumber Actual Exam –Most Tested Questions
with Verified Answers & Rationales | Latest 2026–2027
Edition | Instant PDF Download
Question 1:
The standard residential water pressure should not exceed _______ psi to prevent
damage to plumbing systems.
A. 80
B. 100
C. 60
D. 120
Answer: 60
Rationale: Excessive pressure can damage pipes, fixtures, and appliances.
Question 2:
A _______ is installed in a closed water system to absorb excess pressure caused
by thermal expansion.
A. Trap
B. Check valve
C. Expansion tank
D. Pressure-reducing valve
Answer: Expansion tank
Rationale: Expansion tanks prevent overpressure from heated water.
Question 3:
The minimum slope for a 3-inch horizontal drain line should be _______ per foot
according to plumbing codes.
A. 1/16 inch
B. 1/4 inch
C. 1/8 inch
D. 1/2 inch
Answer: 1/4 inch
Rationale: Proper slope ensures effective drainage and prevents clogging.
Question 4:
A _______ valve allows water to flow in only one direction, preventing backflow
in potable water systems.
A. Gate
B. Check
,C. Globe
D. Ball
Answer: Check
Rationale: Check valves prevent contamination by allowing flow in only one
direction.
Question 5:
The main water shutoff valve is typically located at the point where water _______
the building.
A. Exits
B. Enters
C. Circulates
D. Bypasses
Answer: Enters
Rationale: This placement allows the entire building’s water supply to be isolated
in emergencies.
Question 6:
Which pipe material is commonly used for underground sewer and drainage lines
because it is corrosion-resistant and durable?
A. Copper
B. Galvanized steel
C. PVC
D. PEX
Answer: PVC
Rationale: PVC is ideal for underground drainage due to its durability and
resistance to corrosion.
Question 7:
A _______ valve is installed on water heaters to release excess pressure or
temperature and prevent explosions.
A. Relief
B. Gate
C. Check
D. Globe
Answer: Relief
Rationale: Temperature and pressure relief (T&P) valves ensure safety by
releasing excess heat or pressure.
, Question 8:
PEX piping is joined using _______ or push-fit fittings, which provide leak-free
and flexible connections.
A. Solder
B. Threaded
C. Crimp
D. Weld
Answer: Crimp
Rationale: Crimp or push-fit fittings are standard methods for connecting PEX
tubing.
Question 9:
An air admittance valve allows air to enter a drain line without the vent extending
through the _______.
A. Wall
B. Roof
C. Floor
D. Attic
Answer: Roof
Rationale: AAVs prevent trap siphoning and sewer gas entry while remaining
inside the building.
Question 10:
The minimum diameter of a residential building sewer is _______ inches to ensure
proper waste flow.
A. 2
B. 3
C. 4
D. 6
Answer: 4
Rationale: Code requires a 4-inch minimum for adequate drainage.
Question 11:
A water hammer is caused by a sudden _______ of water flow, which creates a
pressure surge in the pipes.
A. Increase
B. Decrease
C. Stoppage
D. Redirection
with Verified Answers & Rationales | Latest 2026–2027
Edition | Instant PDF Download
Question 1:
The standard residential water pressure should not exceed _______ psi to prevent
damage to plumbing systems.
A. 80
B. 100
C. 60
D. 120
Answer: 60
Rationale: Excessive pressure can damage pipes, fixtures, and appliances.
Question 2:
A _______ is installed in a closed water system to absorb excess pressure caused
by thermal expansion.
A. Trap
B. Check valve
C. Expansion tank
D. Pressure-reducing valve
Answer: Expansion tank
Rationale: Expansion tanks prevent overpressure from heated water.
Question 3:
The minimum slope for a 3-inch horizontal drain line should be _______ per foot
according to plumbing codes.
A. 1/16 inch
B. 1/4 inch
C. 1/8 inch
D. 1/2 inch
Answer: 1/4 inch
Rationale: Proper slope ensures effective drainage and prevents clogging.
Question 4:
A _______ valve allows water to flow in only one direction, preventing backflow
in potable water systems.
A. Gate
B. Check
,C. Globe
D. Ball
Answer: Check
Rationale: Check valves prevent contamination by allowing flow in only one
direction.
Question 5:
The main water shutoff valve is typically located at the point where water _______
the building.
A. Exits
B. Enters
C. Circulates
D. Bypasses
Answer: Enters
Rationale: This placement allows the entire building’s water supply to be isolated
in emergencies.
Question 6:
Which pipe material is commonly used for underground sewer and drainage lines
because it is corrosion-resistant and durable?
A. Copper
B. Galvanized steel
C. PVC
D. PEX
Answer: PVC
Rationale: PVC is ideal for underground drainage due to its durability and
resistance to corrosion.
Question 7:
A _______ valve is installed on water heaters to release excess pressure or
temperature and prevent explosions.
A. Relief
B. Gate
C. Check
D. Globe
Answer: Relief
Rationale: Temperature and pressure relief (T&P) valves ensure safety by
releasing excess heat or pressure.
, Question 8:
PEX piping is joined using _______ or push-fit fittings, which provide leak-free
and flexible connections.
A. Solder
B. Threaded
C. Crimp
D. Weld
Answer: Crimp
Rationale: Crimp or push-fit fittings are standard methods for connecting PEX
tubing.
Question 9:
An air admittance valve allows air to enter a drain line without the vent extending
through the _______.
A. Wall
B. Roof
C. Floor
D. Attic
Answer: Roof
Rationale: AAVs prevent trap siphoning and sewer gas entry while remaining
inside the building.
Question 10:
The minimum diameter of a residential building sewer is _______ inches to ensure
proper waste flow.
A. 2
B. 3
C. 4
D. 6
Answer: 4
Rationale: Code requires a 4-inch minimum for adequate drainage.
Question 11:
A water hammer is caused by a sudden _______ of water flow, which creates a
pressure surge in the pipes.
A. Increase
B. Decrease
C. Stoppage
D. Redirection
