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Quizzes > Science

Plumbing Practice Test for the Master Plumber Exam

Quick quiz with realistic plumbing test questions. Instant results.

Editorial: Review CompletedCreated By: Tiffany RichardUpdated Aug 28, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration for plumbing practice test quiz on a sky blue background

This plumbing practice test helps you check your knowledge for the Master Plumber exam and spot weak areas before test day. After you finish, try our plumbing quiz to refresh basics, and explore a focused boiler exam practice test to build confidence on related systems.

Which backflow prevention device provides protection against both backsiphonage and backpressure for high hazard (health hazard) conditions?
Hose bibb vacuum breaker (HBVB)
Reduced pressure principle assembly (RPZ/RPBA)
Atmospheric vacuum breaker (AVB)
Dual check valve without atmospheric port
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Type L copper tube is best identified by which color marking and typical wall thickness relative to other types?
Black; wall the thinnest of all copper types
Red; wall thicker than Type L
Green; wall thicker than Type K
Blue; wall thicker than Type M and thinner than Type K
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In a DWV system, the purpose of a trap seal is primarily to
Equalize water pressure at fixtures
Increase fixture flow rate
Prevent sewer gases from entering the building
Reduce water hammer in supply lines
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When sizing a domestic water heater, which load unit is most commonly used in plumbing codes for fixture demand?
Kilovolt-amperes
Fixture units
Horsepower
Cubic feet per minute
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Which device must never be installed on the discharge line of a temperature and pressure relief valve on a water heater?
A dielectric union
A drip leg
A 90-degree elbow
A shutoff valve or any obstruction
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The minimum required cleanout size for a 4-inch building drain is typically
3 inches
4 inches
6 inches
2 inches
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For a 1-inch copper water service at 60 psi static pressure, installing a pressure-reducing valve is generally recommended when street pressure regularly exceeds
120 psi
60 psi
80 psi
50 psi
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What is the minimum air gap for a sink faucet outlet above the flood level rim when subject to backsiphonage risk, per common model plumbing codes?
At least 1.5 times the spout reach
At least 2 times the effective opening diameter
Exactly 1 inch regardless of opening size
At least 4 inches in all cases
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For horizontal drainage piping 3 inches in diameter, what is the standard minimum slope to maintain self-cleansing velocity?
1/8 inch per foot (1 percent)
1/4 inch per foot (2 percent)
3/8 inch per foot (3 percent)
1/16 inch per foot (0.5 percent)
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A thermal expansion tank on a closed potable water system should be installed
On a fixture branch farthest from the heater
On the TPR discharge line
On the cold water supply to the water heater, between the shutoff valve and the heater
On the hot water outlet after the mixing valve
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In storm drainage design, what is the primary factor used to size roof drains under the IPC?
Average annual precipitation
Design rainfall rate (in/hr) and roof area
Number of stories in the building
Wind speed category
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In natural gas piping, what is the typical manifold (outlet) pressure for low-pressure residential appliances?
11 inches water column for natural gas
7 inches water column for natural gas
3.5 inches water column for natural gas
2 psi for natural gas
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The minimum vertical distance between a standpipe opening and the top of the clothes washer is primarily intended to
Meet electrical bonding requirements
Increase pump efficiency
Prevent overflow and siphoning by ensuring an air break
Reduce suds accumulation
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A grease interceptor should be sized based on
Flow rate and retention time for the fixture load
Dining area seating count only
Diameter of the building sewer
Water heater capacity
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Which joining method is required for brazing copper tube used on medical gas or high-temperature applications?
Soft solder with water-soluble flux only
No filler metal; rely on capillary action alone
Filler metal with minimum 15 percent silver content and nitrogen purge
Lead-based solder with rosin flux
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What is the maximum allowable pressure for an air test on plastic DWV systems, unless otherwise specified by the authority having jurisdiction?
5 psi for 15 minutes
3 psi for 30 minutes
10 psi for 10 minutes
15 psi for 30 minutes
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When installing PEX tubing, which fitting system allows for the smallest flow restriction due to full expansion of the tube over the fitting?
ASTM F1960 cold expansion with PEX-a
Push-to-connect fitting
Brass compression ferrule
Barb and clamp ASTM F2098
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In cross-connection control, an atmospheric vacuum breaker must be installed
Below the flood level rim for best performance
Upstream of all shutoff valves
Downstream of the last shutoff valve and at least 6 inches above the highest downstream outlet
Horizontally at any elevation relative to outlets
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Under the IPC, a combination waste and vent system is most appropriate for
Floor sinks and floor drains with high flow and low trap seal loss
Grease waste only
Stormwater leaders
Water closets on upper floors
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In a two-pipe steam heating system with a condensate return, the purpose of a steam trap at the radiator outlet is to
Hold back steam while allowing condensate to pass
Reduce boiler pressure
Vent air into the room
Increase steam velocity
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Study Outcomes

  1. Understand core plumbing principles -

    After completing the plumbing practice test, you'll grasp essential Master Plumber concepts including codes, formulas, and system functionalities.

  2. Identify system components -

    You'll recognize common plumbing parts and their roles to accurately address real-world scenarios and mock test questions.

  3. Apply problem-solving techniques -

    You'll use industry-standard calculations and troubleshooting methods to solve practice plumbing exam challenges.

  4. Analyze diagnostic scenarios -

    You'll evaluate symptoms of leaks, blockages, and failures to determine root causes and effective repairs.

  5. Reinforce safety and compliance -

    You'll review best practices and code requirements to ensure safe, code-compliant installations and repairs.

  6. Develop exam strategies -

    You'll refine time management, question analysis, and test-taking skills to boost confidence for the master plumber practice exam.

Cheat Sheet

  1. Hydraulic Fundamentals -

    Master Bernoulli's principle and the Hazen-Williams equation (Q=0.442 C D2.63 S0.54) to predict pressure loss and flow in pipes. For example, using C=130 for new copper lines helps you calculate GPM and pressure drop per 100 ft (Source: IPC & ASPE). Practicing these calculations is a staple of any plumbing practice test or master plumber practice exam.

  2. Fixture Unit Load Calculations -

    Learn how to convert fixture count into Drainage Fixture Units (DFUs) using IPC tables to size drain and vent stacks correctly. For instance, a 1.6 GPM toilet equals 3 DFUs and a lavatory equals 1 DFU, so you'd sum these to pick the right pipe diameter. Mnemonic: "Get FACT" (Fixture count Adds Cumulative Total) to remember to tally all fixtures.

  3. Venting and Trap Protection -

    Review trap seal depths, vent sizing, and maximum trap arm lengths - e.g., a 1¼″ trap arm can be up to 30″ to the vent (IPC Section 906). Remember that proper venting prevents siphoning and sewer gas entry; practice sketching vent diagrams. A quick trick: "SPiT" (Slope, Pitch, Trap) helps you recall key venting factors.

  4. Backflow Prevention Devices -

    Differentiate between reduced pressure zones (RPZ), double check assemblies (DCA), and air gaps, including required test intervals (typically annual). Use the "DCAV" mnemonic: DCA, RPZ, Air gap, Vacuum breaker - to recall device types and code requirements (ANSI/ASSE standards). Questions on your plumbing mock test often focus on application scenarios and maintenance checks.

  5. Water Hammer & Thermal Expansion -

    Understand how sudden valve closure creates pressure surges and how shock absorbers or expansion tanks mitigate water hammer and thermal expansion. For example, install a 2 Gal expansion tank ahead of a water heater to absorb thermal growth (ASTM F1120 guides sizing). This concept shows up in many practice plumbing exams under system protection.

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