Home Inspector Test Home Inspector Plumbing DWV Systems 5 — Questions and Answers
Question 1: When inspecting a two-story home, the inspector finds that a second-floor bath drain connects directly to the vent stack above the first-floor drain connection. What is this arrangement called?
- Wet venting (Correct answer)
- Wet tapping
- Back venting
- Yoke venting
Correct answer: Wet venting
Wet venting is when a single pipe serves as both a drain and a vent, which is permitted under specific code conditions for certain fixture combinations.
Question 2: A home inspector notices that a vent pipe terminates in an attic rather than penetrating through the roof. What is the deficiency?
- Attic vents are permitted if the attic is ventilated
- Sewer gases will accumulate in the attic, creating a health hazard (Correct answer)
- The pipe diameter must be increased in the attic
- Attic terminations require a larger cap
Correct answer: Sewer gases will accumulate in the attic, creating a health hazard
Vent pipes must terminate outdoors above the roofline; terminating in an attic allows toxic sewer gases to accumulate in the structure.
Question 3: What is the purpose of a 'relief vent' in a drainage system?
- To relieve water pressure in supply lines
- To provide additional air circulation to prevent pressure buildup in long horizontal runs (Correct answer)
- To allow cleanout access at the base of a stack
- To connect two parallel drain stacks
Correct answer: To provide additional air circulation to prevent pressure buildup in long horizontal runs
A relief vent connects a drain stack to a vent stack partway up to relieve air pressure differentials in tall or complex drainage systems.
Question 4: During a home inspection, the inspector tests all drains and finds that the kitchen sink drains slowly while all other fixtures drain normally. What is the most likely cause?
- The main sewer line is partially blocked
- There is a localized blockage in the kitchen sink drain or trap (Correct answer)
- The vent stack is completely blocked
- The kitchen drain pipe is undersized
Correct answer: There is a localized blockage in the kitchen sink drain or trap
A slow drain isolated to one fixture points to a local clog in that fixture's trap or branch drain rather than a main line or vent issue.
Question 5: Which of the following pipe materials is most resistant to chemical drain cleaners and is commonly used for residential DWV systems in modern construction?
- Lead
- Cast iron
- PVC Schedule 40 (Correct answer)
- Galvanized steel
Correct answer: PVC Schedule 40
PVC Schedule 40 is the standard material for residential DWV systems; it is chemically resistant, lightweight, affordable, and code-approved.
Question 6: An inspector observes that a 3-inch horizontal drain pipe has a slope of 1/2 inch per foot. What concern should the inspector note?
- The slope is too shallow and will cause slow drainage
- The slope is too steep and solids may separate from liquid, causing clogs (Correct answer)
- A 3-inch pipe requires a minimum 1/2-inch slope
- There is no concern; 1/2 inch per foot is always acceptable
Correct answer: The slope is too steep and solids may separate from liquid, causing clogs
Excessive slope causes water to run ahead of solids, leaving waste behind to accumulate and eventually clog the pipe.
Question 7: A home inspector finds black staining and soft drywall around the base of a soil stack in the basement. Which deficiency does this most likely indicate?
- Condensation from the cold pipe surface
- A leak at a pipe joint allowing sewage to contact the structure (Correct answer)
- Normal discoloration from cast iron oxidation
- A blocked vent causing back-pressure
Correct answer: A leak at a pipe joint allowing sewage to contact the structure
Black staining and soft drywall near drain piping strongly suggest an active or past sewage leak at a joint, requiring immediate professional repair.
Home Inspector Test Home Inspector Plumbing DWV Systems 5
When inspecting a two-story home, the inspector finds that a second-floor bath drain connects directly to the vent stack above the first-floor drain connection.
What is this arrangement called?