Home Inspector Plumbing DWV Systems Questions and Answers

Question 1

During a home inspection, you observe a kitchen sink drain that makes a 'gurgling' sound after water has been drained and a faint sewer gas odor is present.
What is the MOST likely cause of these issues?

Accepted Answer

A blocked or improperly installed vent stack.

Answer

The drain line has an excessive slope.

Answer

The P-trap is installed backward.

Answer

The supply line water pressure is too high.

Question 2

What is the generally accepted minimum slope for a horizontal 3-inch drainpipe in a residential DWV system according to most plumbing codes?

Accepted Answer

1/8 inch per foot

Answer

1/2 inch per foot

Answer

1/4 inch per foot

Answer

1/16 inch per foot

Question 3

A home inspector identifies a sink drain with an 'S-trap' configuration. Which of the following statements BEST describes the issue with this type of trap?

Accepted Answer

It is susceptible to self-siphoning, which can remove the water seal.

Answer

It is more prone to clogging than a P-trap.

Answer

It does not allow for the connection of a mechanical vent.

Answer

It is constructed from materials that are no longer approved for plumbing use.

Question 4

What is the primary purpose of a P-trap in a plumbing drain waste and vent (DWV) system?

Accepted Answer

To hold a small amount of water to block sewer gases.

Answer

To increase the velocity of the wastewater.

Answer

To provide an easy access point for drain cleaning.

Answer

To filter out large debris before it enters the main sewer line.

Question 5

While inspecting a newly installed bathroom sink, you notice the trap arm, which is a 1 1/2-inch pipe, connects to the vent stack only 2 inches from the trap weir. This installation is a defect because:

Accepted Answer

The vent connection is too close, creating a prohibited crown vent.

Answer

The trap arm must be at least 6 inches long.

Answer

The trap arm must slope upwards towards the vent.

Answer

A 1 1/2-inch pipe is too small for a bathroom sink.

Question 6

Which of the following would NOT be considered a component of a residential Drain-Waste-Vent (DWV) system?

Accepted Answer

Pressure relief valve on a water heater.

Answer

Vent stack terminating through the roof.

Answer

P-trap under a kitchen sink.

Answer

Horizontal cast iron soil pipe in the crawlspace.

During a home inspection, you observe a kitchen sink drain that makes a 'gurgling' sound after water has been drained and a faint sewer gas odor is present.What is the MOST likely cause of these issues?

During a home inspection, you observe a kitchen sink drain that makes a 'gurgling' sound after water has been drained and a faint sewer gas odor is present.
What is the MOST likely cause of these issues?