InterNACHI Plumbing Systems Inspection 2 — Questions and Answers
Question 1: What is the minimum slope required for horizontal drain pipes 3 inches or smaller in diameter?
- 1/16 inch per foot
- 1/8 inch per foot
- 1/4 inch per foot (Correct answer)
- 1/2 inch per foot
Correct answer: 1/4 inch per foot
Horizontal drain pipes 3 inches or smaller must slope at least 1/4 inch per foot to ensure proper drainage by gravity.
Question 2: Which type of pipe is NOT approved for use as a water supply line under current plumbing codes?
- PEX
- Copper
- Polybutylene (Correct answer)
- CPVC
Correct answer: Polybutylene
Polybutylene (PB) pipe was recalled and is no longer approved due to its tendency to fail and leak, especially at fittings.
Question 3: A home inspector observes that the water heater's temperature and pressure relief valve discharge pipe terminates into a bucket. This is:
- Acceptable if the bucket is plastic
- A deficiency requiring correction (Correct answer)
- Required by code in some states
- Acceptable if the valve is tested annually
Correct answer: A deficiency requiring correction
The TPR valve discharge pipe must terminate within 6 inches of the floor, into a drain, or to the exterior — never into a bucket or container.
Question 4: What does 'water hammer' refer to in a plumbing system?
- Corrosion buildup inside steel pipes
- A banging noise caused by sudden water flow stoppage (Correct answer)
- Low water pressure at fixtures
- Excessive mineral deposits in a water heater
Correct answer: A banging noise caused by sudden water flow stoppage
Water hammer is a pressure surge or banging noise that occurs when flowing water is abruptly stopped, often by fast-closing valves.
Question 5: An inspector finds galvanized steel supply pipes in an older home. The most likely concern is:
- The pipes are too large in diameter
- Internal corrosion reducing water flow and pressure (Correct answer)
- Galvanized pipe is incompatible with copper fittings only
- These pipes require annual flushing
Correct answer: Internal corrosion reducing water flow and pressure
Galvanized steel pipes corrode from the inside over time, restricting flow, reducing pressure, and eventually leaking.
Question 6: Which condition indicates a failed wax ring seal beneath a toilet?
- The toilet rocks slightly side to side
- Water stains or soft flooring around the toilet base (Correct answer)
- The toilet flushes slowly
- The tank refills loudly after flushing
Correct answer: Water stains or soft flooring around the toilet base
Water stains, soft flooring, or odors around the toilet base indicate a failed wax ring allowing sewer gases and water to escape.
Question 7: What is the purpose of an air admittance valve (AAV) in a drain system?
- To add air pressure to increase drain flow
- To allow air into the drain to prevent siphoning of trap seals without venting through the roof (Correct answer)
- To release excess pressure from drain lines
- To filter odors from plumbing vents
Correct answer: To allow air into the drain to prevent siphoning of trap seals without venting through the roof
An AAV is a one-way valve that opens to admit air when negative pressure develops in the drain, preventing trap siphoning without a conventional vent pipe.
InterNACHI Plumbing Systems Inspection 2
What is the minimum slope required for horizontal drain pipes 3 inches or smaller in diameter?