North Carolina Plumbing Practice Test (Free)

Question 1

What is the general purpose of an air gap on a dishwasher or similar fixture connection?

Accepted Answer

To provide a physical break that prevents backflow or contamination of the potable water supply

Answer

To reduce noise from the pump

Answer

To increase drain flow speed

Answer

To insulate the drain line

Question 2

A cross-connection in a plumbing system generally refers to:

Accepted Answer

Any point where the potable water supply could connect to a source of contamination

Answer

A vent pipe that ties into another vent pipe

Answer

A drain that crosses under a foundation wall

Answer

Two hot water lines joined together

Question 3

What is the primary purpose of a water hammer arrestor in a supply system?

Accepted Answer

To absorb the shock wave created when a fast-closing valve suddenly stops flowing water

Answer

To prevent backflow into the public main

Answer

To increase overall water pressure

Answer

To heat water before it reaches fixtures

Question 4

Why are dielectric unions commonly installed where copper and galvanized steel piping connect?

Accepted Answer

To reduce galvanic corrosion between dissimilar metals

Answer

To allow the pipe to expand with heat

Answer

To filter particulates from the water

Answer

To increase water flow rate

Question 5

What is the primary purpose of a water heater's temperature and pressure relief (T&P) valve?

Accepted Answer

To release water automatically if temperature or pressure exceeds safe limits

Answer

To increase water pressure for faster heating

Answer

To filter sediment from incoming water

Answer

To mix hot and cold water at the fixture

Question 6

In North Carolina, what is the main purpose of a P-trap under a sink?

Accepted Answer

To hold a water seal that blocks sewer gases from entering the room

Answer

To increase drain flow speed

Answer

To filter grease from wastewater

Answer

To vent the drain to the roof

Question 7

What is the general term for the minimum downward slope required on a horizontal drain pipe so waste flows properly by gravity?

Accepted Answer

Pitch or fall

Answer

Superheat

Answer

Subcooling

Answer

Static head

Question 8

What is the general purpose of a fixture's trap seal depth requirement in most plumbing codes?

Accepted Answer

To ensure enough standing water remains to block sewer gas even after minor evaporation or siphoning

Answer

To increase water pressure at the fixture

Answer

To reduce the amount of pipe needed

Answer

To speed up drainage

Question 9

In a typical residential plumbing system, what is the function of a shutoff valve located at each fixture supply line?

Accepted Answer

To allow water service to that fixture to be stopped without shutting off the whole building

Answer

To vent sewer gas from that fixture

Answer

To increase pressure to that fixture only

Answer

To heat water locally at the fixture

Question 10

What does the term 'fixture unit' represent in DWV sizing calculations?

Accepted Answer

A relative measure of the discharge load a fixture places on the drainage system

Answer

The trap seal depth in inches

Answer

A single physical fixture regardless of its water use

Answer

The number of vents required per floor

North Carolina Plumbing Practice Test

Question 1

What is the general purpose of an air gap on a dishwasher or similar fixture connection?

Question 2

A cross-connection in a plumbing system generally refers to:

Question 3

What is the primary purpose of a water hammer arrestor in a supply system?

Question 4

Why are dielectric unions commonly installed where copper and galvanized steel piping connect?

Question 5

What is the primary purpose of a water heater's temperature and pressure relief (T&P) valve?

Question 6

In North Carolina, what is the main purpose of a P-trap under a sink?

Question 7

What is the general term for the minimum downward slope required on a horizontal drain pipe so waste flows properly by gravity?

Question 8

What is the general purpose of a fixture's trap seal depth requirement in most plumbing codes?

Question 9

In a typical residential plumbing system, what is the function of a shutoff valve located at each fixture supply line?

Question 10

What does the term 'fixture unit' represent in DWV sizing calculations?

Question 11

What is the purpose of a cleanout installed in a building drain or sewer line?

Question 12

Why does a drain, waste, and vent (DWV) system need vent piping in addition to drain piping?

Question 13

What condition does a pressure-reducing valve (PRV) address on a residential water supply?

Question 14

What is the general purpose of a vacuum breaker installed on an outdoor hose bibb?

Question 15

Why do plumbing codes generally require backflow prevention devices on irrigation systems connected to the potable water supply?