PC Inspection & Quality Control 3 — Questions and Answers
Question 1: During a gas piping pressure test, the inspector requires holding 1.5 times the working pressure for at least 10 minutes with no pressure drop. What does any pressure drop indicate?
- Normal pressure equalization
- A leak in the gas piping system (Correct answer)
- Faulty gauge calibration only
- Acceptable pipe expansion
Correct answer: A leak in the gas piping system
Any measurable pressure drop during a gas piping test indicates a leak that must be located and repaired before the system can pass inspection.
Question 2: A plumber installs a backflow preventer on a lawn irrigation system. Which document does the inspector typically require to confirm it was tested?
- Manufacturer's installation manual
- A certified backflow test report from a licensed tester (Correct answer)
- The plumbing permit application
- The local water utility pressure record
Correct answer: A certified backflow test report from a licensed tester
Most jurisdictions require a certified tester to perform and document a functional test of backflow preventers at installation and annually thereafter.
Question 3: Which of the following pipe materials requires an inspector to look for dielectric unions at connections to dissimilar metals?
- PVC to ABS
- Copper to galvanized steel (Correct answer)
- PEX to copper
- CPVC to PVC
Correct answer: Copper to galvanized steel
Copper and galvanized steel create a galvanic couple that accelerates corrosion; dielectric unions electrically isolate them to prevent this.
Question 4: What is the inspector verifying when checking that a floor drain has a trap primer connection in a commercial building?
- That the drain meets the minimum 4-inch diameter requirement
- That the trap seal will be maintained even when the drain is rarely used (Correct answer)
- That the drain is connected to a separate sanitary line
- That a backflow valve is installed downstream
Correct answer: That the trap seal will be maintained even when the drain is rarely used
Trap primers periodically add water to infrequently used floor drain traps to prevent the trap seal from evaporating and allowing sewer gas entry.
Question 5: An inspector rejects a shower installation because the mortar bed slopes toward the wall instead of the drain. What defect does this cause?
- Insufficient hot water delivery
- Water pooling against the wall, leading to moisture damage and mold (Correct answer)
- Excessive drain flow rate
- Inadequate water pressure at the showerhead
Correct answer: Water pooling against the wall, leading to moisture damage and mold
A shower floor must slope uniformly toward the drain at ¼ inch per foot; reverse slope traps water at walls, causing leaks and mold behind tile.
Question 6: Which inspection finding would require a plumber to re-pipe a section of supply line rather than simply adding supports?
- Copper tubing supported every 8 feet instead of every 6 feet
- Lead-based solder used on potable water supply lines in a residential renovation (Correct answer)
- Type L copper used instead of Type M in a residential application
- PEX installed in a crawlspace with UV-blocking insulation
Correct answer: Lead-based solder used on potable water supply lines in a residential renovation
Lead-based solder on potable water lines is prohibited; the affected section must be cut out and re-soldered with lead-free (≤0.2% lead) solder.
Question 7: What is the inspector confirming when verifying that a sanitary tee is installed in the correct orientation on a horizontal-to-vertical drain transition?
- That the hub faces upstream
- That the branch inlet points upward to receive flow from fixtures, not downward (Correct answer)
- That the fitting is the correct diameter
- That a cleanout plug is installed in the unused port
Correct answer: That the branch inlet points upward to receive flow from fixtures, not downward
A sanitary tee installed on its back (hub pointing down) on a horizontal run is prohibited because it causes turbulence and can block solids; it must be used only in vertical-to-horizontal transitions.
PC Inspection & Quality Control 3
During a gas piping pressure test, the inspector requires holding 1.5 times the working pressure for at least 10 minutes with no pressure drop.
What does any pressure drop indicate?