InterNACHI Plumbing Systems Inspection 3 — Questions and Answers
Question 1: During a home inspection, the inspector notices the main water shutoff valve is a gate valve that is difficult to turn. The inspector should:
- Force it fully closed to test it
- Note it as a deficiency and recommend evaluation by a plumber (Correct answer)
- Ignore it since gate valves are rarely used
- Replace it on the spot with a ball valve
Correct answer: Note it as a deficiency and recommend evaluation by a plumber
A difficult-to-operate main shutoff is a safety concern and should be noted; the inspector should not force it, as it may break.
Question 2: What is a 'p-trap' designed to do?
- Prevent backflow in the water supply
- Hold water to block sewer gases from entering the home (Correct answer)
- Filter debris from drain lines
- Regulate water pressure at fixtures
Correct answer: Hold water to block sewer gases from entering the home
A p-trap holds a water seal that blocks sewer gases and vermin from entering the living space through the drain opening.
Question 3: What is the maximum temperature the water heater thermostat should be set to in order to prevent scalding while also inhibiting Legionella bacteria growth?
- 100°F
- 110°F
- 120°F (Correct answer)
- 140°F
Correct answer: 120°F
120°F is the commonly recommended setting that balances scald prevention with inhibiting Legionella growth, per most health and safety guidelines.
Question 4: An inspector finds that a washing machine drain hose is inserted more than 4 inches into the standpipe. This creates a risk of:
- Vibration damage to the standpipe
- Back-siphonage of contaminated water into the machine (Correct answer)
- Overloading the drain system
- Excessive noise during the drain cycle
Correct answer: Back-siphonage of contaminated water into the machine
Inserting the drain hose too deep into the standpipe can create a siphon that draws contaminated drain water back into the washing machine.
Question 5: Which of the following best describes 'cross-connection' in plumbing?
- Two pipes of different materials joined together
- A physical link where potable water may be contaminated by non-potable sources (Correct answer)
- A pipe that crosses over another pipe
- A connection between hot and cold supply lines
Correct answer: A physical link where potable water may be contaminated by non-potable sources
A cross-connection is any actual or potential link between the potable water supply and a source of contamination or pollution.
Question 6: What does the presence of active corrosion (green staining) at copper pipe joints indicate?
- The pipes were recently installed
- Pinhole leaks or ongoing moisture at the joint (Correct answer)
- High water hardness in the area
- The pipes are lead-free
Correct answer: Pinhole leaks or ongoing moisture at the joint
Green staining (verdigris) at copper joints indicates active or past moisture, suggesting a slow leak or pinhole corrosion that warrants further evaluation.
Question 7: An inspector observes a plumbing vent pipe that terminates inside an attic rather than through the roof. This is:
- Acceptable if the attic is well-ventilated
- A defect that allows sewer gases to accumulate in the attic (Correct answer)
- Permitted by code if the vent is 12 inches above the insulation
- Only a concern if the attic is conditioned space
Correct answer: A defect that allows sewer gases to accumulate in the attic
Plumbing vents must terminate to the exterior, typically through the roof; terminating inside an attic allows toxic and flammable sewer gases to accumulate.
InterNACHI Plumbing Systems Inspection 3
During a home inspection, the inspector notices the main water shutoff valve is a gate valve that is difficult to turn.
The inspector should: