FREE Master Plumber Drainage Waste Venting Questions and Answers

Question 1

Which of the following scenarios is most likely to result in the siphoning of a fixture trap seal?

Accepted Answer

A stoppage in the main building drain downstream of a vented fixture, causing negative pressure.

Answer

Excessive air intake through an adequately sized vent pipe.

Answer

A properly installed and functioning backflow preventer on the fixture's water supply.

Answer

The fixture's drain being connected directly to a public sewer without an interceptor.

Question 2

What is the primary function of a 'continuous vent' in a drainage system?

Accepted Answer

To serve as the individual vent for a fixture and also as a wet vent for other fixtures.

Answer

To provide an additional source of cleanout access for the drain pipe.

Answer

To allow for the indirect connection of a fixture to the drainage system.

Answer

To provide a continuous pathway for sewer gases to escape directly to the atmosphere without obstruction.

Question 3

A plumber is installing a new island sink in a commercial kitchen. Which specialized venting method is typically required for an island fixture where a conventional vertical vent is impractical?

Accepted Answer

A loop vent (or island vent).

Answer

A branch vent.

Answer

A common vent.

Answer

A circuit vent.

Question 4

According to most plumbing codes, what is the maximum permissible number of drainage fixture units (DFUs) that can be connected to a 2-inch horizontal drainage pipe?

Accepted Answer

6 DFU

Answer

1 DFU

Answer

2 DFU

Answer

8 DFU

Question 5

What is the primary purpose of a 'relief vent' in a drainage system?

Accepted Answer

To provide circulation of air between a vent stack and a drainage stack, especially in multi-story buildings.

Answer

To provide an emergency overflow for fixtures.

Answer

To prevent backflow into the potable water supply.

Answer

To allow direct connection of a fixture without a trap.

Question 6

During a plumbing inspection, it is observed that a section of a horizontal drainage pipe has a grade (slope) of 1/16 inch per foot. What is the most likely consequence of this inadequate slope?

Accepted Answer

Reduced velocity of wastewater flow, leading to solids deposition and stoppages.

Answer

Increased water pressure at the fixture outlets.

Answer

Improved self-scouring action of the pipe.

Answer

Over-venting, causing rapid evaporation of trap seals.