North Carolina Plumbing Practice Test (Free)

Question 1

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

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

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 4

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 5

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 6

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 7

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 8

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 9

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 10

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

Accepted Answer

To prevent contaminated water from being siphoned back into the potable supply

Answer

To increase outdoor water pressure

Answer

To speed up hose drainage

Answer

To heat outdoor water lines in winter

North Carolina Plumbing Practice Test

Question 1

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

Question 2

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

Question 3

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

Question 4

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

Question 5

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

Question 6

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

Question 7

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

Question 8

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

Question 9

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

Question 10

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

Question 11

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

Question 12

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

Question 13

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

Question 14

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

Question 15

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