Home Inspector Test Home Inspector Plumbing DWV Systems 3 — Questions and Answers
Question 1: Which type of vent connects a fixture drain to the main vent stack without requiring its own separate vent pipe penetrating the roof?
- Individual vent
- Wet vent (Correct answer)
- Circuit vent
- Relief vent
Correct answer: Wet vent
A wet vent serves as both a drain and a vent for one fixture while providing venting for another, reducing the number of roof penetrations needed.
Question 2: During inspection, a home inspector notes that a vent pipe terminates 6 inches above the roof surface. What is the concern?
- The pipe is too high and may whistle in wind
- The pipe may be covered by snow or debris, blocking the vent (Correct answer)
- Six inches exceeds the maximum allowed height
- The pipe needs a rain cap
Correct answer: The pipe may be covered by snow or debris, blocking the vent
Most codes require vent pipes to extend at least 6 inches above the roof, but in snow country a minimum of 12 inches is often required to prevent blockage.
Question 3: A home inspector finds that a kitchen sink drain connects to the dishwasher drain without a high loop or air gap. What is the deficiency?
- The connection reduces water pressure
- Wastewater can back-siphon into the dishwasher (Correct answer)
- The drain pipe diameter is incorrect
- The connection violates fire code
Correct answer: Wastewater can back-siphon into the dishwasher
Without a high loop or air gap, contaminated drain water can back-flow into the dishwasher, creating a cross-connection health hazard.
Question 4: What is the maximum distance allowed between a fixture trap and its vent connection for a 1.5-inch drain pipe?
- 2.5 feet
- 3.5 feet (Correct answer)
- 5 feet
- 8 feet
Correct answer: 3.5 feet
For a 1.5-inch pipe, the trap-to-vent distance (trap arm length) is limited to 3.5 feet to prevent siphoning of the trap seal.
Question 5: Which of the following best describes an 'air admittance valve' (AAV) in a DWV system?
- A one-way valve that allows air in but not sewer gas out (Correct answer)
- A pressure relief device on the water heater
- A backwater valve preventing sewer backflow
- A vacuum breaker on a hose bib
Correct answer: A one-way valve that allows air in but not sewer gas out
An AAV is a spring-loaded, one-way mechanical vent that opens to admit air when negative pressure develops in the drain, eliminating the need for a traditional vent pipe.
Question 6: A home inspector observes a 4-inch cast iron soil stack that has significant horizontal crackling and scaling on its exterior. What is the recommended action?
- Apply a sealant coat immediately
- Note it as a material deficiency and recommend evaluation by a licensed plumber (Correct answer)
- This is normal aging and requires no action
- Replace only the visible section
Correct answer: Note it as a material deficiency and recommend evaluation by a licensed plumber
Exterior scaling and cracking of cast iron indicates corrosion and potential structural failure; a licensed plumber should evaluate for replacement.
Question 7: Which fitting type is required when making a direction change from vertical to horizontal in a drain line?
- 90-degree elbow (street ell)
- Long-sweep 90-degree or two 45-degree fittings (Correct answer)
- Tee fitting with cap
- Reducer bushing
Correct answer: Long-sweep 90-degree or two 45-degree fittings
Long-sweep 90s or two 45-degree fittings are required for vertical-to-horizontal transitions to maintain flow velocity and reduce clogging risk.
Home Inspector Test Home Inspector Plumbing DWV Systems 3
Which type of vent connects a fixture drain to the main vent stack without requiring its own separate vent pipe penetrating the roof?