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Mississippi Plumbing Licensing Exam — Practice Test

What This Practice Exam Covers

The Mississippi Plumbing licensing exam is 70 questions, 180 minutes, and requires a 70% to pass. That's 49 correct answers minimum.

This practice exam gives you two ways to prepare:

Free practice exam — 10 questions per attempt, pulled from a limited pool. You can retake it as many times as you want. Use it to get a feel for question style and difficulty before committing to full prep.

Full practice exam (paid) — 70 questions, 180-minute timer, same format as the real test. Questions are drawn from a pool of 412+ items, so each attempt gives you a different set. No duplicate exams. Coverage matches the exact topic breakdown provided by the official test provider. If you're serious about passing on the first try, start here after you've tried the free version.

What You'll Be Tested On

The exam covers 14 topic areas. Here's what each one actually demands from you.

Drain, Waste, and Vent (15 items) — The heaviest section. You need to know drainage fixture unit (DFU) values, slope requirements for horizontal runs, vent types (individual, common, wet, circuit, air admittance valves), and trap rules. Expect to size pipes using IPC Table 710.1(1) and Table 710.1(2), and to identify prohibited trap types. One wrong assumption about slope or DFU loading can cascade into a wrong answer.

Isometric Analysis (12 items) — Pure calculation. You'll work from isometric drawings to find center-to-center lengths, cut lengths, and 45-degree offset travel using the 1.414 constant. Rolling offsets and three-pipe diagrams appear too. Bring your math — these questions can't be guessed. Mathematics for Plumbers and Pipefitters Units 9–34 cover these methods directly.

Water Supply (6 items) — Backflow prevention selection, water service pipe materials, system sizing, cross-connection protection, hot water temperature controls, and valve placement. You'll need to distinguish between air gaps, reduced-pressure principle assemblies, double-check valves, and vacuum breakers — and know which hazard level calls for which device. Reference IPC 2021, Table 608.1 for device selection.

Fixtures and Equipment (5 items) — Minimum fixture counts by occupancy, installation clearances, water closet requirements, shower compartment construction, and temperature control at fittings. Know ICC A117.1 Section 604.4 for water closet clearances and Section 602.2.3 for lavatory requirements.

General Plumbing Regulations (4 items) — Material standards, system protection (freezing, corrosion, structural damage), trenching and bedding requirements, pipe support intervals by material type per Table 308.5, and required tests. Section 312.5 covers the basic water test; Section 312.2 covers air testing.

Safety (4 items) — Confined space classification, permit requirements, atmospheric testing, and the distinct roles of entry supervisors, attendants, and authorized entrants. 29 CFR §1926.21(b)(2) covers safety training requirements; 29 CFR §1926.651(g)(1)(i) covers excavation atmospheres. Know PPE selection and employer responsibilities cold.

Cleanouts (4 items) — Placement intervals for horizontal drains, building drains, and sewers; required clearances from openings to obstructions; cleanout size relative to pipe size (IPC Section 708.1.5); approved plug materials and head types. Understand when a 4-inch cleanout satisfies a larger pipe run.

Traps and Interceptors (4 items) — Trap seal depth, prohibited trap types, distance limits from trap to vent, double-trapping prohibition, and grease interceptor sizing. Grease interceptor questions often involve specific facility types. Know IPC Section 1003.3.2 for grease interceptors and Section 1002.1 for trap seal requirements.

Piping, Valves, Controls (3 items) — Approved materials for water service and drainage, joint methods by pipe type, valve placement, backflow devices, and pressure-reducing valve requirements. IPC 2021, Section 603.1 and Table 604.3 are frequently cited.

Hangers and Supports (3 items) — Support intervals by material (horizontal and vertical), hanger material requirements, galvanic action prohibitions, sway bracing at direction changes, and seismic support. Table 308.5 is the key reference.

Joints and Connections (3 items) — Methods for PVC, copper, cast iron, and ABS; transition between dissimilar materials; prohibited joints in sanitary systems. Know when solvent cement, press-connect, mechanical coupling, or caulked joints apply.

Backflow (3 items) — Definitions, device selection by hazard level, installation requirements including critical level and freeze protection, and annual inspection/testing standards. Overlaps with Water Supply — study them together.

Water Heaters (2 items) — T&P relief valve installation per IPC 2021, Section 504.1; discharge piping specs per Section 504.7; pan requirements; drain valve requirements; and access clearances per Section 502.3.

Developed Length (2 items) — Center-to-center vs. end-to-end measurements, fitting allowances for threaded, copper, and plastic fittings, and converting measurements to cut lengths. Mathematics for Plumbers Unit 8 covers threaded allowances; Units 9–12 cover copper and plastic.

Worked Sample Questions

Question 1 — Cleanouts

When a cleanout is installed on a 6-inch drainage pipe, what is the minimum required size of that cleanout?

• A. 6 inches
• B. 2 inches
• C. 3 inches
• D. 4 inches

Correct Answer: D — 4 inches

IPC Section 708.1.5 requires cleanouts to match the pipe they serve — except when the pipe exceeds 4 inches in diameter. In that case, the cleanout does not need to be larger than 4 inches. A 6-inch pipe gets a 4-inch cleanout, not a 6-inch one. Candidates who read the rule too quickly assume "same size as pipe" and pick A. Read the exception.

Question 2 — Isometric Analysis

A 45-degree offset has a set of 16 inches. Using a constant of 1.414, what is the travel? Select the closest answer.

• A. 20-1/4"
• B. 22-5/8"
• C. 24-3/4"
• D. 26-1/8"

Correct Answer: B — 22-5/8"

For a 45-degree offset: Travel = Set × 1.414

16 × 1.414 = 22.624 inches

22.624 inches converts to 22-5/8" (22.625"). That's your answer. If you picked C or D, you likely multiplied by the wrong constant. The 1.414 constant is for 45-degree travel only — don't confuse it with the run constant (1.000 at 45 degrees, since run equals set).

Question 3 — Water Supply

Under the International Plumbing Code, what is the minimum depth below ground surface from which a private potable well may be developed, and how far above the well platform must the casing extend?

• A. 5 feet below ground; 4 inches above the platform
• B. 10 feet below ground; 6 inches above the platform
• C. 10 feet below ground; 12 inches above the platform
• D. 15 feet below ground; 6 inches above the platform

Correct Answer: B — 10 feet below ground; 6 inches above the platform

IPC 2021 Sections 608.18.3 and 608.18.4 set both requirements. The water table must be at least 10 feet below ground surface, and the watertight casing must extend at least 10 feet below ground and 6 inches above the well platform. Option C adds an extra 6 inches above the platform that the code doesn't require — that's the distractor.

How to Read Your Score

Passing requires 70% — 49 out of 70 questions correct.

Your first practice attempt is a diagnostic, not a verdict. A score of 60–65% tells you which topics need work, not that you can't pass. A score below 60% on the first try is normal if you haven't opened the code yet.

After each attempt, look at your score by topic. The exam weights Drain, Waste, and Vent at 15 items and Isometric Analysis at 12 items — together that's nearly 39% of the test. If you're losing points in those two areas, fix them first. They're also the most recoverable: both are rule-based or math-based, not judgment calls.

Scoring 72–74% on practice usually means you're at the margin on the real exam. A bad testing day or one unfamiliar question can push you under. Aim for 80%+ on practice before you schedule the real test. Use the 412+ question pool to keep seeing fresh questions — retaking the same 10 questions until you memorize the answers isn't preparation.

Where Candidates Lose Points

Isometric math errors — Wrong constant, arithmetic slip, or forgetting to subtract fitting allowances. These 12 questions reward careful written work. Do the math on paper; don't estimate.

DFU miscounts — Drain, Waste, and Vent questions often require you to total fixture units before sizing a pipe. One wrong DFU value throws off the whole calculation. Know IPC Table 709.1 by fixture type.

Cleanout size on large pipes — Candidates miss the 4-inch cap in IPC Section 708.1.5 and mark "same size as pipe" for 6-inch and 8-inch runs.

Backflow device selection — Confusing a pressure vacuum breaker with a reduced-pressure principle assembly, or misidentifying the hazard level. Each device has a specific application. IPC 2021, Table 608.1 lays this out — memorize it.

Safety role confusion — Mixing up the duties of entry supervisors, attendants, and authorized entrants under 29 CFR §1926.21(b)(2) and related sections costs points on the Safety topic.

Running out of time — 180 minutes for 70 questions is about 2.5 minutes per question. Isometric questions take longer. Practice your pacing so the math questions don't eat your time budget.

Exam Quick Facts