Practice test

Free Plumbing Practice Test

Take our free plumbing practice test with 20 questions covering water supply, drainage and vent systems, and plumbing code. See your score instantly.

These questions are for study practice only and are not official exam questions.

Question 1

1

What is the purpose of a vent pipe in a drain-waste-vent (DWV) system?

Question 2

2

An air admittance valve (AAV) may NOT be used as the sole vent termination for an entire building's drainage system because:

Question 3

3

What device is installed on a water supply line to prevent contaminated water from flowing backward into the potable supply?

Question 4

4

In a wet-vented system, what is generally required of the pipe that serves as both drain and vent simultaneously?

Question 5

5

The maximum horizontal distance a trap arm may travel before connecting to a vent is limited to prevent:

Question 6

6

A horizontal drain pipe sloped more steeply than 1/2 inch per foot is generally discouraged for large-diameter pipes because:

Question 7

7

Fixture unit values are used in plumbing design primarily to:

Question 8

8

A building's incoming water service pipe is undersized, causing a significant pressure drop under peak demand. Which is the BEST corrective action?

Question 9

9

A building has a measured static pressure of 50 psi at street level. Water loses approximately 0.43 psi per vertical foot of elevation. If the top-floor fixture is 60 feet above the meter, what is the approximate static pressure available at that fixture before any friction losses?

Question 10

10

Which pipe material is most commonly used for residential cold-water supply lines in modern construction?

Question 11

11

What is the primary purpose of a P-trap beneath a plumbing fixture?

Question 12

12

Which type of trap is prohibited by most plumbing codes because it retains solids, is difficult to vent properly, and has an unreliable seal?

Question 13

13

What is the minimum slope typically required for a horizontal drain pipe that is 3 inches or smaller in diameter?

Question 14

14

Which fitting is prohibited in the horizontal plane of a drain line because it creates an abrupt direction change that allows solids to accumulate?

Question 15

15

The term 'cross-connection' in plumbing refers to:

Question 16

16

What term describes the minimum vertical distance between a water outlet and the flood-level rim of a fixture that prevents backflow by creating a physical break?

Question 17

17

A cleanout fitting in a drainage system is primarily installed to:

Question 18

18

What condition causes a trap seal to be lost when the fixture itself drains so rapidly that the moving water column pulls the seal water out behind it?

Question 19

19

Water hammer in supply piping is best controlled by installing:

Question 20

20

When sizing a cold-water branch using the fixture-unit method, what additional factor must be accounted for beyond the total fixture unit count?

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