2026 Edition

Master Plumber Practice Exam

Take this free master plumber practice test to study for your master plumber licensing exam. Our plumbing test prep is written by plumbing instructors who are master plumbers. For more comprehensive practice, use our Master Plumber Practice Test. See the links below for free plumbing flash cards and a free plumbing study guide.

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General Regulations

1 Code interpretation is a critical element of success when working with the code requirements and regulations. Who does the code authorize to interpret the plumbing code?

a. A master plumber

b. An architect

c. A licensed code enforcement officer

d. Both a and c

Incorrect. Please choose another answer.

c - Of the possible answers, only the licensed code officer is the one who is allowed to interpret the code. Whether a plumbing installation passes or fails an inspection is subject to a code officer's interpretation. You can appeal a decision that you feel is incorrect or questionable. Even as a master plumber your understanding of the intent of the code is not absolute. The plumbing inspector is the final word in the field when it comes to an interpretation of the code.

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2 What is the purpose of the plumbing code?

a. To generate revenue for a jurisdiction through fees

b. To control the plumbing work

c. To protect the plumbing industry from unlicensed plumbers

d. To have a legally enforceable document to safeguard property and public welfare

Incorrect. Please choose another answer.

The main purpose of a plumbing code is to safeguard the health, safety, property and public welfare of a community. It becomes legally enforceable when it is adopted by a governing body with jurisdiction.

3 When will a less stringent local plumbing code supersede state and federal codes?

a. Never

b. On minor plumbing work only

c. On Installation instructions from the manufacturer

d. Only on new construction work

Incorrect. Please choose another answer.

The provisions of a local plumbing code will not be deemed to supersede state or federal law unless they exceed the requirements of the state or federal law, making the local requirement more stringent. This occurs only if the state or federal authority permits preemption.

Administrative Policies

4 Which of the following plumbing fixtures requires a plumbing permit and inspection for the replacement of the fixture in the same exact location?

a. Toilet

b. Bidet

c. Bathtub

d. Water heater

Incorrect. Please choose another answer.

d - Water heaters require that you apply for and receive a plumbing permit prior to the replacement of an existing water heater. After the replacement work is completed you must arrange for a plumbing inspection of the work by a code enforcement officer. All other plumbing fixtures can be replaced in their exact locations without the need for a permit or inspection. Due to the risk that can arise from a faulty installation of a water heater it is the rare fixture that does require a permit and inspection for a simple replacement.

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5 The plumbing code applies to new installations. Which of the following types of plumbing work may also be governed by the code?

a. Renovations

b. Replacement of plumbing fixtures

c. Additions to a plumbing system

d. All of the above

Incorrect. Please choose another answer.

All new installations are required to comply with the plumbing code. Other elements that may be required to meet current code requirements can include renovations, the replacement of fixtures, additions to a plumbing system and extensive repairs to plumbing systems. At no time can work done to a plumbing system make it unsafe or be detrimental to the system.

Fixtures

6 Assume that you have been contracted to add a new bathroom group to an existing plumbing system. This is a toilet, lavatory and bathtub that will be installed in a new addition to a home. You will need a permit for the installation. Your plan is to connect the main drain from the bathroom group to the building drain. This could create a problem. From the choices below, choose the most likely concern.

a. The building drain may need replaced with a larger pipe.

b. Requirements for accessible plumbing fixtures

c. Minimum distance requirements between fixtures

d. The fact that water fountains cannot be installed in a room that contains a toilet

Incorrect. Please choose another answer.

Adding new plumbing fixtures can overload existing plumbing. You must compute the total fixture-unit ratings and the demand that it will put on existing plumbing piping. It is possible that an existing pipe might have to be removed and replaced with a larger pipe.

7 What is the minimum number of plumbing fixtures that must be installed in a single-family residence?

a. 3

b. 4

c. 5

d. 6

Incorrect. Please choose another answer.

The minimum number of plumbing fixture required for a single-family home is five. This includes a toilet, a lavatory, a bathing unit, a kitchen sink and a washing machine connection. Additional fixtures can be added, such as dishwashers and hose bibs.

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8 You are installing accessible plumbing fixtures. You had journeyman plumbers set the fixtures and you review the work prior to calling for a code enforcement inspection. Visually, something looks wrong to you. Your concern is that the faucets on the lavatories will be difficult to reach for disabled people. Using your tape measure, you check the distance from the front of the lavatory. What is the maximum distance that a lavatory faucet for accessible use can be placed from the front edge of a lavatory?

a. 18 inches

b. 22 inches

c. 24 inches

d. 25 inches

Incorrect. Please choose another answer.

Twenty-five inches is the maximum distance allowed between the front edge of a lavatory and the faucet installed on it when the fixture is to be rated as an accessible fixture.

Indirect & Special Wastes

9 Discharge tubing connected to a relief valve does not require traps for which of the following?

a. A water heaters

b. A boiler

c. An expansion tank that serves a boiler

d. All of the above

Incorrect. Please choose another answer.

The discharge tubing that is connected to a relief valve that is servicing a water heater, boiler or an expansion tank for a boiler is not allowed to be trapped. Discharge piping from the relief valve is to extend downward to a point within six inches of a floor. Ideally, the drainage tubing should terminate above a floor drain, but this is not a requirement. The end of the tubing is not to be threaded.

10 What is the maximum allowable water temperature that can be used with a commercial dishwashing machine?

a. 115 degrees F.

b. 120 degrees F.

c. 140 degrees F.

d. None of the above

Incorrect. Please choose another answer.

Commercial dishwashing machines are allowed to use high-temperature hot water that would not be allowed for a residential use. It is common for these machines to use hot water that has a temperature in excess of 140 degrees F. 165 degrees F is what is needed to sanitize 99.9% of bacteria according to NSF 3. Due to the high temperature of hot water used with commercial equipment the discharge from the dishwasher must discharge through either an air gap or an air break. The discharge is to enter a standpipe made of approved materials for the high-temperature water.

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Vents

11 Circuit vents may be _____________.

a. Connected to stack vents

b. Connected to vent stacks

c. Connected to a main vent system that extends to outside air

d. All of the above

Incorrect. Please choose another answer.

Circuit vents are allowed to tie into stack vents, vent stacks and venting systems that extend to outside air. They may also extend to outside air independently.

12 When you are required to size a waste stack vent you will need to know ____________.

a. The type of fixtures that will connect to the pipe

b. The flow rate of the pipe

c. The number of drainage fixture units that the pipe will be required to handle

d. The developed length of the vent piping

Incorrect. Please choose another answer.

Drainage fixture units are the primary key needed to size waste stack vents. Once you have this, you will have a chart to work with to convert your information into a minimum pipe diameter for the piping. You will need to determine the total discharge of fixture units into one branch interval. The total discharge into the pipe, measured in fixture units, is also needed. With this in hand and the proper sizing chart, you will be able to cross reference from the chart to determine the minimum diameter of the stack size.

Traps and Cleanouts

13 What is the maximum distance that cleanouts can be installed from an access opening under a floor, such as in a crawl space?

a. 4 feet

b. 7 feet

c. 20 feet

d. 50 feet

Incorrect. Please choose another answer.

There cannot be more than twenty feet between an access opening and a cleanout when the cleanout is installed below a finished floor. More than one access opening may have to be provided for access to cleanouts in large buildings.

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14 What is the minimum depth of a trap seal?

a. 1 inch

b. 1.25

c. 1.5 inches

d. 2 inches

Incorrect. Please choose another answer.

The minimum depth of a liquid trap seal is two inches. This depth must be maintained. If the trap is not used often the trap seal may evaporate. If there is a risk of the trap drying out, a trap prime is to be installed. This is a device that detects a falling level of liquid in a trap and then introduces water into the trap if the trap seal is in risk of dropping below the required minimum.

Waste Water and Distribution

15 What is the maximum allowable flow rate and consumption for a lavatory installed for public use with a pressure rating requirement of 60 PSI?

a. 0.5 gpm

b. 1 gpm

c. 2.5 gpm

d. 3 gpm

Incorrect. Please choose another answer.

Public lavatories that are required to deliver waster at a pressure of 60 psi are required to have a maximum flow rate and consumption of 0.5 gpm. This does not seem like much water. Water conservation has long been a concern and newer fixtures are designed to operate properly while using less water.

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