Master Plumber Exam Drainage, Waste, and Venting 3

Question 1

What is the minimum diameter of a vent stack that serves a building drain receiving discharge from 5 or more water closets?

Accepted Answer

4 inches

Answer

The IPC requires a minimum 4-inch vent stack when the building drain receives discharge from 5 or more water closets.

Question 2

A combination drain and vent system is limited to which type of fixtures?

Accepted Answer

Floor drains and floor sinks only

Answer

Combination drain and vent systems under the IPC are restricted to floor drains and floor sinks due to their low flow rates.

Question 3

When a horizontal branch drain connects to a stack between the lowest floor branch and the building drain, what is this zone called?

Accepted Answer

Critical zone

Answer

The critical zone is the area at the base of the stack where high-velocity waste creates pressure fluctuations that can affect trap seals.

Question 4

What is the maximum number of fixture units permitted on a 2-inch horizontal branch drain?

Accepted Answer

6

Answer

The IPC allows a maximum of 6 fixture units on a 2-inch horizontal branch drain at a 1/4-inch per foot slope.

Question 5

Which venting method allows multiple fixtures on a horizontal branch to share a single vent at the end of the branch?

Accepted Answer

Circuit venting

Answer

Circuit venting uses one vent at the end or beginning of a horizontal branch to serve multiple fixtures connected to that branch.

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