Start Practice Test

Idaho Plumbing Contractor Exam — Practice Test & Study Guide

What This Practice Exam Covers

The Idaho Plumbing Contractor Exam consists of 100 questions answered within 240 minutes. A passing score is 75%, meaning you must answer at least 75 questions correctly. The exam draws from 23 topic areas spanning the 2017 Idaho State Plumbing Code (Chapters 2, 5–12), gas piping, plumbing system sizing with schematics, and the Contractor's Business and Law Reference Manual covering employment law, insurance, safety, contracts, and more.

This site offers two ways to prepare:

• Free practice exam: 10 questions per attempt, drawn from a limited pool. You can retake it as many times as you like — it's a genuine sample of the question style and format, and a good first step before committing to deeper study.
• Full practice exam (paid): 100 questions, 240-minute time limit — an exact mirror of the real exam structure. Questions are drawn from a pool of 883+ items, so every attempt generates a unique exam. No two sittings are identical, which means repeated attempts build real breadth rather than memorized sequences.

Start with the free exam to calibrate where you stand, then use the full exam to drive your preparation.

What You'll Be Tested On

2017 Idaho State Plumbing Code — Code Chapters

Chapter 2 — Definitions (1 item): A single question, but definitions show up implicitly everywhere. Know the precise meanings of drainage terms (building drain, soil pipe, stack, horizontal branch), vent system terms (dry vent, wet vent, stack vent, yoke vent, relief vent), backflow terms (air gap, backsiphonage, cross-connection, critical level), and trap terms (trap seal, crown weir, top dip). The exam will use these terms in questions across other chapters — misreading a definition early cascades into wrong answers later.

Chapter 5 — Water Heaters (5 items): Expect questions on water heater location restrictions (prohibited in bedrooms, bathrooms without specific conditions), TPR valve requirements under 2017 ISPC Section 504.6, combustion air calculation methods (indoor, outdoor, mechanical, and combined), and vent type selection (Type B, Type L, single-wall metal, direct-vent). Vent termination clearances and the permit/inspection process for water heater installation are also tested.

Chapter 6 — Water Supply and Distribution (5 items): Cross-connection control is a priority. Know which backflow prevention assembly — air gap, AVB, PVB, SVB, double-check (DC), or reduced-pressure (RP) — applies to each hazard level. Section 601.3.1, 601.3.2, and 601.3.3 address potable/nonpotable system identification and labeling. Questions also cover approved pipe materials, joining methods (soldered, brazed, flared, mechanical, heat-fusion), pressure regulator requirements, expansion tanks, and shutoff valve placement under Sections 603.4.3, 603.5.1, and 604.2.

Chapter 7 — Drainage (2 items): Know drainage fixture unit (DFU) values by fixture type, minimum drain pipe slopes (typically 1/4 inch per foot for pipes under 3 inches), approved materials for underground versus aboveground drainage, cleanout spacing and access requirements under Section 707.9, and how to read maximum unit loading tables for drain sizing per Section 710.1.

Chapter 8 — Indirect Waste (5 items): This chapter is weighted more heavily than many candidates expect. Air gap versus air break distinctions (Sections 801.2, 801.3.1–801.3.3), standpipe receptor dimensions under Section 804.1, condensate waste disposal and pipe sizing under Sections 814.1 and 814.2, and food-service equipment indirect waste requirements are all fair game. Know the pipe size and length limits for indirect waste piping under Section 803.3.

Chapter 9 — Vents (5 items): Vent pipe sizing requires reading tables based on fixture units and developed length. Know vent pipe grades and how vents must connect to drain pipes (Section 906.1.1, 906.2). Idaho-specific rules on vent termination — roof clearances, frost and snow closure requirements, sidewall venting — appear in the question bank. Wet venting configurations for bathroom groups (Section 908.2.2) and air admittance valve limitations (Sections 911.1, 911.2) are Idaho-specific nuances that show up.

Chapter 10 — Traps (3 items): Know prohibited trap types (S-traps, bell traps, crown-vented traps) per Section 1002.3, trap seal depth minimums and maximums per Section 1001.2, trap arm length limits under Section 1004.1, and floor drain trap primer requirements. Building trap installation conditions are covered under Sections 1009.3 and 1016.4.

Chapter 11 — Storm Drainage (2 items): Sizing roof drains and vertical conductors using rainfall rate tables, sizing horizontal storm drains by projected area, and primary versus secondary drainage system requirements under Sections 1101.3, 1101.6, and 1104.1 are all testable.

Chapter 12 — Gas Piping (4 items): Approved materials, sizing methods (longest length per IFGC Section 402.4.1, branch length per Section 402.4.2), underground installation requirements, pressure testing procedures (test medium, pressure, duration), and appliance connections including sediment traps and shutoff valve placement are all covered. Know Section 1201.1 for scope and Section 1208.1.1 for pressure testing basics.

Plumbing Sizing Using Schematics (8 items): Eight questions — one of the heaviest single topic blocks — require you to work from a schematic provided during the exam. You must calculate water supply fixture units (WSFU), size pipe and meter given pressure and developed length, assign DFU values, size drain and vent piping from maximum unit loading tables, and size storm drainage from rainfall rates. Treat this as applied math with open-book tables; slow, systematic work beats rushing.

Contractor's Business and Law Reference Manual — Business and Law Topics

Sections 6 (20 items), 7 (15 items), and 11 (10 items) together account for 45 of the 100 exam questions — nearly half the test.

Section 6 — Employment Law (20 items): Federal anti-discrimination laws (Title VII, ADA, ADEA, EPA, GINA, Pregnancy Discrimination Act), FMLA eligibility and leave entitlements including military caregiver leave, FLSA wage and hour requirements and exemptions, Davis-Bacon prevailing wage, Copeland Anti-Kickback Act weekly statement requirements, Service Contract Act, Walsh-Healey Act, and Idaho-specific wage payment statutes (§45-608 through §45-613) and new hire reporting.

Section 7 — Insurance and Bonding (15 items): Workers' compensation employer requirements and exemptions (corporate officer, casual employment), unemployment insurance experience rating, surety bond types (bid, performance, payment bonds), the Miller Act threshold for federal public works, independent contractor classification for UI tax purposes, and insurance types including CGL, builder's risk, completed operations, EPLI, and pollution liability.

Section 11 — OSHA and Safety (10 items): OSHA recordkeeping forms (300, 300-A, 301), inspection priorities, fall protection thresholds, PPE requirements by hazard, hearing protection triggers, scaffold requirements, hazard communication, and excavation safety under 29 CFR 1926.652(a)(1).

Sections 3, 4, 5, 8, 9, 10, 12, 13 (1–4 items each): Business entity types, DOPL licensing requirements, financial statements and ratios, lien rights and filing deadlines under Idaho Title 45, construction contracts, estimating methods, and tax obligations round out the exam.

Worked Sample Questions

Question 1

Under the Family and Medical Leave Act, how many workweeks of leave are available during a single 12-month period to care for a covered service member with a serious injury or illness?

• A. 26 workweeks
• B. 12 workweeks
• C. 20 workweeks
• D. 16 workweeks

Correct Answer: A — 26 workweeks

Standard FMLA leave for qualifying family or medical reasons is 12 workweeks. Military caregiver leave is a distinct, expanded entitlement: an eligible employee who is the spouse, son, daughter, parent, or next of kin to a covered service member receives up to 26 workweeks during a single 12-month period. Candidates who confuse this with standard FMLA leave will choose B and lose the point. Source: Contractor's Business and Law Reference Manual, Section 6 — Family and Medical Leave Act (FMLA), Military Caregiver Leave

Question 2

A subcontractor defaults on a bonded public job. Which bond protects the owner by guaranteeing project completion?

• A. Bid bond
• B. Performance bond
• C. General liability
• D. Builder's risk

Correct Answer: B — Performance bond

A bid bond only guarantees that a bidder will enter into contract if awarded the project — it has no role after award. General liability covers third-party bodily injury and property damage. Builder's risk covers physical loss to the structure under construction. A performance bond is the surety instrument that guarantees the contractor will complete the work according to the contract terms; if the contractor defaults, the surety steps in. Source: Contractor's Business and Law Reference Manual, Section 7: Insurance — Bonding, Performance Bond

Question 3

At what continuous noise exposure level must an employer provide hearing protection?

• A. 85 dBA
• B. 90 dBA
• C. 95 dBA
• D. 100 dBA

Correct Answer: A — 85 dBA

OSHA's permissible exposure limit for noise is 90 dBA over an 8-hour time-weighted average (TWA), but the hearing conservation program — which includes providing hearing protectors — is triggered at 85 dBA TWA. Many candidates pick B because 90 dBA is the PEL, but the question asks when protection must be made available, not when exposure becomes impermissible. Source: Contractor's Business and Law Reference Manual, Section 11 / Construction Industry Digest, Hearing Protection section

How to Read Your Score

The passing threshold is 75% — 75 correct answers out of 100. If your first full practice attempt lands below that mark, treat it as diagnostic information, not a verdict on your readiness.

A score below 65% typically signals gaps across multiple topic areas, and a structured review of at least the three heaviest sections — Employment Law (Section 6), Insurance and Bonding (Section 7), and OSHA (Section 11) — should come before your next attempt. These three sections alone represent 45 questions; mastering them is the fastest path to a passing score.

A score between 65% and 74% usually means you have solid coverage in some areas but are losing points in specific code chapters or calculation-heavy topics. Use the topic-by-topic breakdown your practice exam provides to identify exactly which chapters are dragging your score down.

A score at or just above 75% on practice deserves honest scrutiny: a few fortunate guesses on a 100-question exam can put you at the passing line without true command of the material. We recommend targeting 80–85% on full practice exams consistently before scheduling the real test. Scoring well above the minimum on practice gives you a genuine margin of safety on exam day.

Where Candidates Lose Points

Confusing similar code provisions. The most common code errors involve backflow prevention (Chapter 6) — candidates select the wrong device for the hazard level — and indirect waste air gap versus air break distinctions (Chapter 8). These are not interchangeable, and the exam exploits that.

Calculation errors in the schematic sizing section. Eight questions require multi-step calculation — fixture unit totals, pipe sizing table lookups, developed length — and candidates frequently drop a fixture, read the wrong column, or apply the wrong slope. A single wrong input early sends every downstream answer off. Work these problems methodically and double-check unit conversions.

Blending FMLA standard leave with military caregiver leave. Twelve weeks versus 26 weeks is a distinction the exam tests directly. It is one of the most commonly missed employment law questions.

Misidentifying bond types. Bid, performance, and payment bonds have distinct functions. Candidates who blur these distinctions routinely miss Section 7 questions, especially those involving the Miller Act threshold for federal projects.

Running out of time on code chapters. With 240 minutes for 100 questions, that is 2 minutes and 24 seconds per question. The sizing schematic questions and gas piping sizing questions consume more time than average. Candidates who don't pace themselves finish the exam rushing through employment law — their strongest area — and leave points on the table.

Skipping Idaho-specific provisions. AAV limitations, sidewall vent termination rules, and Idaho wage payment statutes (§45-608 through §45-613) differ from generic national standards. Preparing from a national code reference alone leaves these points uncovered.

Exam Quick Facts