Master Plumber Drainage, Waste, and Venting Questions and Answers

Question 1

A master plumber is designing a DWV system for a multi-story building.
A soil stack has a horizontal offset greater than 45 degrees.
According to most model codes, how must the portion of the stack BELOW the offset be sized?

Accepted Answer

Based on the total number of drainage fixture units on the entire stack or the size of the offset, whichever is larger.

Answer

The same size as the portion of the stack above the offset.

Answer

As a straight vertical stack based on the fixture units below the offset.

Answer

One pipe size smaller than the offset itself.

Question 2

When performing a water test on a newly installed plastic DWV system, what is the minimum required head of water that must be applied above the highest point of the system being tested, and for what duration, according to the 2021 IPC?

Accepted Answer

10 feet of head for 15 minutes

Answer

5 feet of head for 10 minutes

Answer

10 feet of head for 10 minutes

Answer

5 feet of head for 15 minutes

Question 3

A plumber is installing an island sink and must use an island fixture vent (loop vent). Which of the following is a mandatory requirement for this type of installation under the Uniform Plumbing Code (UPC)?

Accepted Answer

A 'foot vent' must be taken off the vertical fixture vent immediately below the floor.

Answer

The loop must extend at least 2 inches above the flood-level rim before returning down.

Answer

The vent portion below the floor must be sloped towards the nearest wall.

Answer

The return bend can be constructed using two 90-degree elbows.

Question 4

In which of the following scenarios is a Combination Waste and Vent System most likely to be permitted by the authority having jurisdiction?

Accepted Answer

For floor drains in a large, open-plan grocery store where running conventional vents is structurally impractical.

Answer

For venting a battery of water closets in a commercial restroom.

Answer

In a new residential kitchen with a sink, dishwasher, and food waste disposer.

Answer

To serve as the primary venting method for an entire single-family home.

Question 5

According to the IPC, what is the minimum diameter for any soil or waste stack that receives the discharge from a water closet?

Accepted Answer

3 inches

Answer

2 inches

Answer

4 inches

Answer

2 1/2 inches

Question 6

A horizontal drainage branch connects to the base of a 4-inch drainage stack. According to the IPC, what is the minimum distance downstream from the stack that this horizontal branch connection must be made?

Accepted Answer

40 inches

Answer

20 inches

Answer

10 inches

Answer

8 feet

A master plumber is designing a DWV system for a multi-story building.A soil stack has a horizontal offset greater than 45 degrees.According to most model codes, how must the portion of the stack BELOW the offset be sized?

A master plumber is designing a DWV system for a multi-story building.
A soil stack has a horizontal offset greater than 45 degrees.
According to most model codes, how must the portion of the stack BELOW the offset be sized?