Texas Master Plumber Exam| Questions & Answers & Rationale |
2025/2026 | Latest Update | Instant Download !!
1. A 4-inch building drain connects to a horizontal branch with a slope of ¼ inch per foot. What is the
MAXIMUM number of fixture units allowed to discharge into the branch?
A. 24
B. 42
C. 160 ✔
D. 256
Correct Answer: C
Rationale: Under the IPC/UPC tables adopted in Texas, a 4-inch horizontal branch can carry up to 160
DFUs at minimum slope.
2. A plumber is installing a natural gas system in a commercial kitchen. Which test must be
performed before placing the system into service?
A. Low-pressure air test at 1 psi
B. 3 psi air test for 30 minutes with no drop ✔
C. Hydrostatic test
D. Leak detector spray test only
Correct Answer: B
Rationale: Texas gas code requires a minimum 3 psi air test (or 1½x working pressure) without pressure
loss.
3. A water heater installation requires a thermal expansion tank. Which condition mandates this?
A. Any tank over 20 gallons
B. Any electric heater only
,C. A closed water supply system ✔
D. Any system above 50 psi
Correct Answer: C
Rationale: Thermal expansion devices are required when a check valve or PRV creates a closed system.
4. An indirect waste line must discharge to a receptor. Which installation meets code?
A. Directly into a floor drain
B. Air-gap into a standpipe ✔
C. Direct connection to a trap arm
D. Air-break into a sink basin
Correct Answer: B
Rationale: Food-service and medical indirect waste must discharge via air-gap into a properly trapped
receptor.
5. A 2-inch trap arm is installed horizontally. What is the MAXIMUM distance allowed between trap
weir and vent?
A. 3 ft
B. 5 ft
C. 8 ft ✔
D. 12 ft
Correct Answer: C
Rationale: 2-inch trap arms may run up to 8 ft before venting under UPC/IPC adopted in Texas.
6. A plumber is sizing a gas system with a 100-foot developed length. If the connected load requires
250,000 BTUs, what pipe size is the minimum for a single trunk line?
A. ¾ inch
B. 1 inch
C. 1¼ inch ✔
D. 2 inch
, Correct Answer: C
Rationale: Gas sizing tables show 1¼ inch can handle over 250k BTUs at 100 ft.
7. A pressure relief valve discharge pipe for a water heater must:
A. Be threaded at the termination
B. Reduce down two sizes
C. Discharge by gravity and be full-sized ✔
D. Terminate above ceiling
Correct Answer: C
Rationale: T&P discharge lines must be full-sized, gravity-fed, and terminate properly.
8. A sewer ejector pump serving a basement bathroom requires venting. Which configuration is
correct?
A. Mechanical vent
B. Air admittance valve
C. Separate vent to open air ✔
D. No vent is required
Correct Answer: C
Rationale: Sewage ejectors must be vented directly to the atmosphere.
9. A plumber is installing a 3-inch vent through the roof. What is the minimum roof extension height?
A. 4 inches
B. 6 inches
C. 12 inches ✔
D. 24 inches
Correct Answer: C
Rationale: Vent pipes must extend at least 12 inches above the roof per code.
2025/2026 | Latest Update | Instant Download !!
1. A 4-inch building drain connects to a horizontal branch with a slope of ¼ inch per foot. What is the
MAXIMUM number of fixture units allowed to discharge into the branch?
A. 24
B. 42
C. 160 ✔
D. 256
Correct Answer: C
Rationale: Under the IPC/UPC tables adopted in Texas, a 4-inch horizontal branch can carry up to 160
DFUs at minimum slope.
2. A plumber is installing a natural gas system in a commercial kitchen. Which test must be
performed before placing the system into service?
A. Low-pressure air test at 1 psi
B. 3 psi air test for 30 minutes with no drop ✔
C. Hydrostatic test
D. Leak detector spray test only
Correct Answer: B
Rationale: Texas gas code requires a minimum 3 psi air test (or 1½x working pressure) without pressure
loss.
3. A water heater installation requires a thermal expansion tank. Which condition mandates this?
A. Any tank over 20 gallons
B. Any electric heater only
,C. A closed water supply system ✔
D. Any system above 50 psi
Correct Answer: C
Rationale: Thermal expansion devices are required when a check valve or PRV creates a closed system.
4. An indirect waste line must discharge to a receptor. Which installation meets code?
A. Directly into a floor drain
B. Air-gap into a standpipe ✔
C. Direct connection to a trap arm
D. Air-break into a sink basin
Correct Answer: B
Rationale: Food-service and medical indirect waste must discharge via air-gap into a properly trapped
receptor.
5. A 2-inch trap arm is installed horizontally. What is the MAXIMUM distance allowed between trap
weir and vent?
A. 3 ft
B. 5 ft
C. 8 ft ✔
D. 12 ft
Correct Answer: C
Rationale: 2-inch trap arms may run up to 8 ft before venting under UPC/IPC adopted in Texas.
6. A plumber is sizing a gas system with a 100-foot developed length. If the connected load requires
250,000 BTUs, what pipe size is the minimum for a single trunk line?
A. ¾ inch
B. 1 inch
C. 1¼ inch ✔
D. 2 inch
, Correct Answer: C
Rationale: Gas sizing tables show 1¼ inch can handle over 250k BTUs at 100 ft.
7. A pressure relief valve discharge pipe for a water heater must:
A. Be threaded at the termination
B. Reduce down two sizes
C. Discharge by gravity and be full-sized ✔
D. Terminate above ceiling
Correct Answer: C
Rationale: T&P discharge lines must be full-sized, gravity-fed, and terminate properly.
8. A sewer ejector pump serving a basement bathroom requires venting. Which configuration is
correct?
A. Mechanical vent
B. Air admittance valve
C. Separate vent to open air ✔
D. No vent is required
Correct Answer: C
Rationale: Sewage ejectors must be vented directly to the atmosphere.
9. A plumber is installing a 3-inch vent through the roof. What is the minimum roof extension height?
A. 4 inches
B. 6 inches
C. 12 inches ✔
D. 24 inches
Correct Answer: C
Rationale: Vent pipes must extend at least 12 inches above the roof per code.
