InterNACHI Plumbing & HVAC Systems 4 — Questions and Answers
Question 1: When should a home inspector recommend testing a sump pump during an inspection?
- Only during heavy rain
- By pouring water into the pit to verify the float switch activates the pump (Correct answer)
- By disconnecting the float to test the motor directly
- Only if the basement shows visible water stains
Correct answer: By pouring water into the pit to verify the float switch activates the pump
Pouring water into the sump pit is the standard method to verify the float switch activates and the pump discharges water properly without waiting for rain.
Question 2: What does a home inspector look for when evaluating a gas appliance's combustion air supply?
- The BTU output rating on the appliance label
- Whether adequate air openings exist to support complete combustion (Correct answer)
- The color of the pilot flame
- The length of the flexible gas connector
Correct answer: Whether adequate air openings exist to support complete combustion
Combustion appliances require sufficient air supply to burn fuel completely; inadequate combustion air leads to carbon monoxide production and flame rollout.
Question 3: Which type of drain trap is prohibited by most plumbing codes because it loses its water seal easily?
- P-trap
- S-trap (Correct answer)
- Drum trap
- J-trap
Correct answer: S-trap
S-traps are prohibited because self-siphoning action caused by rapid drainage easily pulls the water seal out, allowing sewer gases to enter the building.
Question 4: An inspector observes black ABS drain pipe that has been repaired with white PVC pipe and a standard coupling. What is the issue?
- The color mismatch is a code violation
- ABS and PVC require a special transition cement, not a standard coupling (Correct answer)
- PVC cannot be used underground
- The pipe diameter must match the original exactly
Correct answer: ABS and PVC require a special transition cement, not a standard coupling
ABS and PVC have different chemical compositions and require a special transition or all-purpose cement to bond; standard ABS or PVC cement will not create a lasting joint between them.
Question 5: What is the typical temperature range at which a residential water heater thermostat should be set to balance scalding prevention and Legionella control?
- 100–110°F
- 115–120°F
- 120–140°F (Correct answer)
- 150–160°F
Correct answer: 120–140°F
The recommended range is 120–140°F; 120°F minimizes scalding risk for most households, while 140°F is advised where Legionella is a concern — with an anti-scald mixing valve at fixtures.
Question 6: Which HVAC component is responsible for moving refrigerant through the system by raising its pressure and temperature?
- Evaporator coil
- Condenser coil
- Compressor (Correct answer)
- Expansion valve
Correct answer: Compressor
The compressor is the heart of the refrigeration cycle, compressing low-pressure refrigerant vapor into high-pressure, high-temperature vapor for heat rejection at the condenser.
Question 7: A home inspector finds that flexible gas connectors behind a gas range pass through the cabinet wall. Why is this a defect?
- Flexible connectors must be stainless steel only
- Flexible connectors must not pass through walls, floors, or ceilings (Correct answer)
- The connector is too short for code compliance
- The connector must have a shutoff valve at each end
Correct answer: Flexible connectors must not pass through walls, floors, or ceilings
Flexible gas connectors are not rated for concealed or enclosed installations and must remain accessible and visible; passing through a wall creates a hidden leak hazard.
InterNACHI Plumbing & HVAC Systems 4
When should a home inspector recommend testing a sump pump during an inspection?