North Carolina Plumbing Practice Test (Free)

Question 1

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 2

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 3

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 4

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

Accepted Answer

Incoming static street pressure that is too high for fixtures and appliances

Answer

Water that is too cold

Answer

Low flow rate at the water meter

Answer

Bacterial contamination in the supply

Question 5

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 6

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

Accepted Answer

To admit air so trap seals are not siphoned or blown out as water drains

Answer

To reduce the diameter of the drain pipe

Answer

To supply fresh water to fixtures

Answer

To heat the wastewater before it leaves the building

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

Accepted Answer

To provide access for clearing clogs without cutting into the pipe

Answer

To increase water pressure in the line

Answer

To vent sewer gas into the attic

Answer

To heat the wastewater

Question 9

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 10

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

Accepted Answer

To stop contaminated water, fertilizer, or soil from being siphoned back into the drinking water system

Answer

To meter water usage for billing

Answer

To increase watering pressure

Answer

To reduce the irrigation system's water bill

North Carolina Plumbing Practice Test

Question 1

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

Question 2

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

Question 3

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

Question 4

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

Question 5

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

Question 6

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

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

Question 9

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

Question 10

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

Question 11

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

Question 12

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

Question 13

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

Question 14

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

Question 15

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