Start Practice Test

Idaho Plumbing Journeyman Exam — Practice Test & Study Guide

What This Practice Exam Covers

The Idaho Plumbing Journeyman licensing exam is 100 questions with a 180-minute time limit. You need to answer 70 of those 100 questions correctly to pass. The exam draws from 17 topic areas rooted entirely in the 2017 Idaho State Plumbing Code (ISPC), plus two schematic-based sizing problems worth 4 points each.

This practice test is available in two formats:

Free practice exam: 10 questions per attempt, pulled from a limited question pool. You can retake it as many times as you like — it costs nothing and gives you an accurate feel for question style, terminology, and code-specific wording before you commit to full prep.

Full practice exam (paid): 100 questions, 180-minute timer — identical structure to the real exam. Questions are drawn from a pool of 1,702+ items, so every attempt produces a unique exam. No two sessions repeat the same set. This is the tool for serious, systematic preparation.

What You'll Be Tested On

Chapter 1 — Administration (5 items)
Expect questions on permit requirements, which work is exempt, how permits are issued and when they expire, and what happens when a permit lapses. You must also know the Authority Having Jurisdiction's (AHJ) powers — including right of entry, stop-work orders, and condemnation authority. Violations and penalties appear here too. Know the distinctions between new installations, alterations, and repairs.

Chapter 2 — Definitions (5 items)
Pure vocabulary. The exam tests precise definitions: the difference between a soil pipe and a waste pipe, between backsiphonage and backpressure, between a vent stack and a stack vent. Know definitions under Sections 204.0, 205.0, 209.0, 210.0, and 211.0. A wrong definition costs you the question outright — there is no partial credit.

Chapter 3 — Materials (5 items)
Know approved pipe and fitting standards, how materials must be marked, and what fittings are prohibited in drainage and vent piping. Support intervals by material type (Tables 313.3 and 313.6), nail plate protection, sleeve requirements through structural members, trench bedding for thermoplastic pipe, and the alternative engineered design approval process all appear here.

Chapter 4 — Fixtures (5 items)
Fixture clearances and spacing, minimum fixture counts by occupancy, and water consumption limits (flow rates for lavatories, showers, water closets, urinals). Shower compartment waterproofing and lining materials show up regularly. Know the rules for flushometer valves and antisiphon flush tanks. Section 408 covers tubs and showers; Section 422.2 covers urinal fixture counts and exceptions.

Chapter 5 — Water Heaters (10 items)
One of the heavier-weighted chapters. Topics include prohibited water heater locations (Section 502.1), temperature and pressure relief valve requirements (Section 504.1(1) and 504.3.2), combustion air sizing methods (Section 506), vent connector materials and clearances (Section 507), Category I appliance venting types, and chimney termination heights. The 3-foot above roofline rule (Section 509.5.4) is a frequently tested specific number.

Chapter 6 — Water Supply and Distribution (11 items)
The largest chapter by item count alongside Chapter 7. Backflow prevention is heavily tested: know the difference between an atmospheric vacuum breaker (AVB), pressure vacuum breaker (PVB), double check valve assembly (DC), and reduced-pressure principle assembly (RP), and which hazard level or condition requires which device (Sections 603.5.1 through 603.5.15). Lead content limits, pipe joining methods by material (copper, CPVC, PEX, PE, PP), pressure regulation, expansion tanks, and fixture-unit-based sizing all appear.

Chapter 7 — Drainage (11 items)
Also 11 items. Know which pipe materials are approved above-grade versus belowground — galvanized steel is specifically prohibited underground per Section 701.2(1). Drainage fixture unit (DFU) values, pipe slope requirements (typically ¼ inch per foot for 3-inch and smaller), cleanout location and spacing rules (Section 708.1), grade requirements for building sewers, and backwater valve and ejector requirements for below-grade fixtures (Sections 712.2 and 712.3) are all fair game.

Chapter 8 — Indirect Waste (6 items)
Air gap versus air break — know the definitions and when each is required. Indirect waste requirements for food service equipment, condensate disposal and overflow protection, chemical and industrial waste pretreatment, and approved piping for those applications. Steam condensate systems and sumps round out this chapter.

Chapter 9 — Venting (10 items)
Vent pipe sizing by fixture units and developed length, roof termination clearances (Section 904.1), the requirement that vents connect above the flood-level rim, wet venting rules for bathroom groups (Section 908.1), circuit venting limits (Section 910.3 and 910.4), island fixture venting (Section 911.1), and air admittance valve restrictions (Section 911.2). Developed length calculations require careful reading.

Chapter 10 — Traps, Interceptors, and Separators (7 items)
Trap arm lengths, prohibited trap types (Section 1002.3), trap seal depth of 2–4 inches (Table 1002.2), grease interceptor sizing for hydromechanical versus gravity units (Sections 1014.1 and 1014.3.6), and sand interceptor design requirements (Section 1017.1 and 1017.2). Know the distinction between a gravity grease interceptor and a hydromechanical grease interceptor from Chapter 2 definitions first.

Chapter 11 — Storm Drainage (4 items)
Sizing roof drains and vertical conductors, sizing horizontal storm drains and sewers, primary versus secondary (emergency) drainage requirements (Sections 1101.12.2.1 and 1101.12.2.2), and subsoil drain discharge options. Controlled-flow roof drainage conditions also appear.

Chapter 12 — Gas Piping (8 items)
Gas pipe sizing methods and allowable pressure drop, approved metallic and plastic materials, underground versus aboveground installation rules (Section 1208.1.1), pressure testing and leak detection procedures (Section 1210.1.1 through 1210.1.7), gas meter placement, pressure regulators, and shutoff valve requirements. Purging procedures are tested as well.

Chapter 14 — Firestopping (1 item)
One question. It will likely address F-rating and T-rating requirements, combustible versus noncombustible pipe penetrations through fire-rated assemblies, annular space firestopping, or the sleeve-and-fill rules (Sections 1402.1, 1404.3, 1405.2).

Chapters 15 and 16 — Alternate Water Sources and Rainwater Catchment (3 items combined)
Gray water system design, cross-connection prevention, signage requirements for nonpotable systems, maintenance log requirements, and rainwater catchment storage tank marking and treatment standards. Water quality minimums and system labeling are tested.

Chapter 17 — Referenced Standards (1 item)
You need to recognize standards organization abbreviations (ASME, ASTM, ASSE, AWWA, NSF, NFPA) and match standards to the correct application — pipe materials, fittings, backflow prevention assemblies, or fixtures. See Table 1701.1.

Plumbing Sizing Schematics (2 items, 4 points each)
Two calculation problems using schematic diagrams provided during the exam. You will assign water supply fixture units, convert to demand flow using Chart A, calculate permissible friction loss per 100 feet, and select pipe diameter using friction loss charts and equivalent pipe length tables. These are worth more per item than any other question — don't skip the Appendix A sizing methodology in your study materials.

Worked Sample Questions

Question 1 — Chapter 6: Backflow Prevention

Which backflow prevention device or assembly is the ONLY acceptable protection for an irrigation system that includes a chemical injector?
A. Atmospheric vacuum breaker (AVB)
B. Double check valve backflow prevention assembly (DC)
C. Pressure vacuum breaker backflow prevention assembly (PVB)
D. Reduced-pressure principle backflow prevention assembly (RP)

Correct Answer: D

When a chemical injector is present, the contamination risk is classified as a high-hazard cross-connection. Only the reduced-pressure principle assembly (RP) provides the required level of protection — it maintains a positive pressure differential between its two check valves and vents to atmosphere if either check fails. Per 2017 ISPC Section 603.5.6.3, where a system includes chemical injection or provisions for it, an RP assembly is mandatory. AVBs and PVBs cannot be used where a continuous pressure condition exists; a DC assembly doesn't provide adequate protection against high-hazard connections.

Question 2 — Chapter 7: Underground Pipe Materials

Galvanized wrought-iron or galvanized steel pipe may be used underground for drainage piping. TRUE or FALSE?

Correct Answer: FALSE

Per 2017 ISPC Section 701.2(1), galvanized wrought-iron and galvanized steel pipe are prohibited underground for drainage piping and must be kept not less than 6 inches above grade. Underground conditions accelerate corrosion of galvanized coatings, making them unsuitable below ground.

Question 3 — Chapter 5: Chimney Termination Height

A chimney for a residential-type appliance shall extend not less than how many feet above the highest point where it passes through the roof?
A. 2 feet B. 3 feet C. 4 feet D. 5 feet

Correct Answer: B

Per 2017 ISPC Section 509.5.4, the chimney must extend at least 3 feet above the roof penetration point. This height ensures adequate draft and prevents exhaust gases from being pulled back down by wind pressure across the roof surface. The "2 feet" option is a distractor — that number appears in other vent termination contexts but not here.

How to Read Your Score

The passing threshold is 70% — 70 correct answers out of 100. If your first practice attempt lands in the 60s, that is a diagnostic result, not a final verdict. It tells you where your knowledge gaps are, not whether you can pass.

Use the topic-by-topic score breakdown as your study plan. If you score well on Chapters 2 and 3 but poorly on Chapters 6 and 7, spend your time in those 22 combined exam items — they represent nearly a quarter of your total score. The schematic sizing problems (Appendix A) are often undertrained; 8 possible points from 2 questions makes them disproportionately important.

A practice score in the 70–74% range generally means you are close but vulnerable on exam day — one bad chapter can drop you below passing. Aim for consistent 80%+ across multiple unique attempts before scheduling the real exam. Because the full practice pool contains 1,702+ questions, each attempt genuinely tests different material, so high scores across multiple attempts are a more reliable indicator than a single strong run.

Start with the free 10-question exam to get oriented, then move to the full 100-question timed exam to simulate real conditions.

Where Candidates Lose Points

Mixing up definitions. Chapter 2 vocabulary losses are avoidable. Candidates confuse vent stack with stack vent, or backsiphonage with backpressure. These terms have specific code definitions — a wrong definition loses the question regardless of how well you know installation practice.

Wrong backflow device for the hazard level. Chapter 6 questions frequently hinge on selecting the correct device for a specific condition. An AVB where a PVB is required, or a DC where an RP is required, is a wrong answer. Know the hierarchy and the conditions that trigger each.

Galvanized pipe underground. This is a known trap — Section 701.2(1) is tested repeatedly and candidates who rely on general trade knowledge instead of the code answer wrong.

Vent sizing developed length. Chapter 9 sizing questions require you to use fixture unit counts and full developed length, not straight-line distance. Candidates who measure incorrectly or apply the wrong table fail these questions.

Skipping the schematic problems. Many candidates skip or rush the Appendix A sizing questions under time pressure. At 4 points each, leaving both blank drops you 8 raw points — nearly half the margin between passing and failing. Practice the full sequence: assign WSFUs, convert to gpm, calculate friction loss, select pipe size.

Running the clock out on Chapters 6 and 7. With 22 combined items and multi-part code cross-references, these chapters can consume 45 or more minutes. Budget your time explicitly before you sit down.

Exam Quick Facts