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Oklahoma Plumbing Journeyman and Natural Gas — Practice Exam Guide

What This Practice Exam Covers

The Oklahoma Plumbing Journeyman and Natural Gas exam consists of 85 questions answered in 180 minutes, with a passing score of 75% (64 correct answers). The exam draws from 10 topic areas spanning IPC code knowledge, gas code regulations, pipe mathematics, and OSHA safety.

Two practice options are available:

• Free practice exam: 10 questions per attempt, drawn from a limited pool. You can retake it as many times as you like — it costs nothing and gives you a solid feel for question style and difficulty before you commit to serious prep.
• Full practice exam (paid): Mirrors the real exam with 85 questions and a 180-minute time limit. Questions are pulled from a pool of 401+ items, so each attempt presents a unique set — no two sittings are identical. Coverage matches the exact topic breakdown provided by the official test provider.

Start with the free exam to get your bearings, then use the full exam for timed, realistic practice.

What You'll Be Tested On

General Plumbing Knowledge and Regulations — 10 items

This is one of the heaviest sections. Questions test the IPC's scope and intent under Section 101.3, permit application procedures under Section 106.2, and what work is exempt from permits. You need to know inspection authority and the types of required system tests. Expect math: pipe length calculations using fitting allowances for threaded, copper, and PVC fittings (center-to-center vs. end-to-end), and offset and diagonal calculations using angle constants — particularly the 45° multipliers (1.414 for diagonal, 0.707 for offset).

Piping, Valves, and Control Valves — 8 items

Know your joining methods across pipe materials. Questions cover approved water supply and distribution materials, as well as fittings and connection standards (see IPC 2018, Tables 605.3 and 605.4). Valve-specific questions focus on pressure-reducing valves, backflow preventers, and relief valves — their types, required locations, and functions. Pipe support and hanger spacing requirements appear here, as does PVC-specific pipe and connection content. Pipe length math (c-c and e-e calculations) also shows up in this section.

Fixtures and Equipment — 8 items

Minimum fixture counts by occupancy classification are tested directly using IPC 2018, Table 403.1 and Section 403.1.1. You must know fixture spacing and clearance requirements (Section 405.3.1), waste outlet sizing for specific fixtures (water closets, lavatories, showers, sinks, urinals), flushing devices, and thermostatic shower valve requirements. Water heater installation and relief valve rules — including Sections 504.2, 504.4.1, 504.6, and 504.7 — appear alongside trap requirements and prohibited trap types under IPC 2018, Section 1002.1.

Water Supply — 10 items

This section is demanding. Backflow prevention is a major focus: know device types, assemblies, and where each applies (IPC 2018, Table 608.1 and Table 608.16.1). Pipe sizing requires understanding flow rates, pressure requirements, and approved materials. Cross-connection control and identification of non-potable systems are tested — particularly Section 608.14.2 and 608.17.6. Pressure booster systems, water hammer arrestors, and thermal expansion control round out the section (see Section 606.5.1 for booster system requirements).

Drains and Sewers — 10 items

Questions focus on drainage pipe materials for above-ground, underground, and building sewer installations (IPC 2018, Table 704.1). Drainage system sizing uses fixture unit values from IPC 2018, Table 709.1 and Table 709.2. You must know slope requirements for horizontal drainage piping (Section 704.1), cleanout location and spacing rules (Sections 708.1.1 through 708.1.10), and sump/ejector design. Backwater valve requirements also appear here.

Vents — 13 items

The largest topic on the exam. Vent pipe sizing and developed length calculations apply across stack vents, vent stacks, and individual, branch, and circuit vents (Table 906.5.1, Section 906.1). You must know termination requirements: roof extension heights and clearances from openings under Sections 903.1, 903.5, and 904.2. Multiple venting methods are tested — wet vents (Section 912.1), circuit vents (Section 914.2 and 914.3), combination waste-and-vent (Section 915.1), island fixture venting (Section 913.2), and single-stack systems (Section 911.3). Air admittance valve rules — installation, location, sizing, and prohibited locations under Sections 918.2 through 918.8 — are frequently tested. Know dry vent grade and connection-above-centerline requirements (Section 905.2 through 905.6).

Traps, Interceptors, Indirect, and Special Waste — 10 items

Trap seal depth, prohibited trap types, and primer devices are tested under IPC 2018, Section 1002.1 through Section 1002.10. Grease interceptor and automatic grease removal device rules appear under Sections 1003.3.2 through 1003.3.8 and Table 1003.3.5.1. Indirect waste piping questions require you to distinguish air gap from air break (Sections 802.1.1 through 802.4.3). Standpipe, waste receptor, and hub drain installation also appear.

Isometric Analysis — 7 items

These questions require you to interpret isometric drawings and perform calculations. Expect c-c and e-e pipe length problems, 45° offset work using the 1.414 diagonal multiplier and 0.707 offset multiplier, three-pipe offset diagrams, and multi-fitting assemblies involving wyes, tee-wyes, and elbows. Fitting allowances for threaded, copper, PVC, and cast iron fittings all appear. Draw on Mathematics for Plumbers and Pipefitters — particularly pages covering Units 47–53 and the isometric analysis chapters.

Fuel Gas — 5 items

Gas pipe sizing using the longest-length and branch-length methods is tested, along with approved piping materials (steel, copper, CSST, polyethylene) and prohibited materials under 2018 IFGC Sections 403.4.1 through 403.6. Pressure drop allowances and maximum operating pressure appear in Section 402.4.1 and 402.7. Vent sizing and termination for gas appliances (Sections 503.5.4, 503.5.6, 503.7.2), combustion air requirements (Sections 304 and 501.8), and appliance installation clearances (Section 501.9) round out this section.

Safety — 4 items

OSHA 29 CFR 1926 regulations govern this section. Know the 6-foot fall protection trigger under §1926.502, personal fall arrest system component specs, guardrail system requirements, and ladder safety rules. PPE questions cover head, eye, face, foot, and hearing protection — including selection, provision, and maintenance standards under §1926.95(b) and §1926.95(d)(2). Safety net installation and inspection requirements also appear.

Worked Sample Questions

Question 1 — Vents

What is the maximum slope permitted for the vent section of a horizontal branch drain in a circuit vent system?

• A. One unit vertical in 8 units horizontal (12.5-percent slope)
• B. One unit vertical in 4 units horizontal (25-percent slope)
• C. One unit vertical in 16 units horizontal (6.25-percent slope)
• D. One unit vertical in 12 units horizontal (8.3-percent slope)

Correct Answer: D

Per IPC 2018, Chapter 9 — Section 914.3, the slope of the vent section of the horizontal branch drain in a circuit vent system shall not be greater than one unit vertical in 12 units horizontal (8.3-percent slope). This is a specific numeric limit — not a general "standard" drainage slope — so candidates who recall the usual ¼" per foot (1:48) slope for drainage piping and apply it here will select wrong answers. Circuit vent systems have their own slope ceiling, and the exam tests exactly that distinction.

Question 2 — General Plumbing Knowledge and Regulations

As a plumbing contractor installing PVC pipe, you need to cut a piece to fit between a 90° ell and a 45° ell with a center-to-center distance of 10 inches. The fitting allowances from the manufacturer are ⁹⁄₁₆" for the 90° ell and ⁵⁄₁₆" for the 45° ell. What is the end-to-end pipe length you should cut?

• A. 10⅞"
• B. 8¾"
• C. 9⅛"
• D. 9⅞"

Correct Answer: C

For PVC pipe, end-to-end (e-e) = center-to-center (c-c) minus total fitting allowance. Add the two fitting allowances: ⁹⁄₁₆" + ⁵⁄₁₆" = ¹⁴⁄₁₆" = ⅞". Subtract from c-c: 10" − ⅞" = 9⅛". PVC fitting allowances work the same way as copper — no extra thread-in calculation is needed. Candidates who confuse PVC with threaded pipe math, or who add rather than subtract the allowances, land on wrong answers. Source: Mathematics for Plumbers and Pipefitters, Pages 48–49.

Question 3 — Water Supply

You are a journeyman plumber called to a 12-story building where tenants on upper floors report inadequate water pressure at fixtures. The street main pressure is too low to serve the upper floors. Which of the following is an approved method to supplement the water supply?

• A. Add a barometric loop at the top floor
• B. Increase the size of the water meter only
• C. Install a water pressure-reducing valve on the main supply riser
• D. Install a hydropneumatic pressure booster system

Correct Answer: D

Per IPC 2018, Section 606.5.1, when street main pressure is insufficient, the supply must be supplemented by an elevated water tank, a hydropneumatic pressure booster system, or a water pressure booster pump. A pressure-reducing valve lowers pressure — it cannot raise it — making option C a common trap. Option B addresses flow rate, not pressure deficit. Option A is a backflow prevention method, not a pressure solution.

How to Read Your Score

The passing threshold is 75% — that means 64 correct out of 85 questions on the real exam.

Your first full practice attempt is best treated as a diagnostic, not a verdict. Most candidates score below passing on their first timed run, and that is normal. What matters is which topics dragged the score down. A topic-by-topic breakdown lets you prioritize: if you're strong on Safety (4 items) but losing points across Vents (13 items) and Drains and Sewers (10 items), that's where your study time returns the most.

A practice score of 65–70% means you have identifiable gaps but are closer than it feels — focused review of two or three weak sections can close that gap. A score of 55% or below suggests the foundational code material needs more work before retesting on the practice exam. A score in the low 80s is encouraging, but the real exam will draw from content your practice attempts haven't yet surfaced from the 401+ question pool — don't stop there.

Retake the full practice exam with different draws to expose as much of the pool as possible before exam day.

Where Candidates Lose Points

Venting math errors are the most costly single source of lost points. With 13 items on the line, confusing developed length with total vent stack height, or applying the wrong sizing table, can alone push a borderline candidate below passing.

Fitting allowance mistakes in multi-step pipe calculations hurt scores across the General Knowledge, Piping, and Isometric Analysis sections. A common error: adding fitting allowances instead of subtracting, or applying threaded pipe math to PVC or copper fittings. These problems look similar but use different procedures.

Wrong backflow preventer type for the application is a repeated trap in the Water Supply section. Table 608.1 and Table 608.16.1 assign specific devices to specific hazard levels — selecting an air gap where a reduced-pressure assembly is required (or vice versa) is a clean miss.

Circuit vent and wet vent rules get conflated. Sections 912.1, 914.2, and 914.3 each carry distinct slope, connection, and fixture count rules that candidates blur together under time pressure.

Fuel gas material prohibitions catch candidates who assume all copper is allowed — IFGC Section 403.4.1 restricts copper in natural gas systems depending on gas type.

Running out of time on isometric drawings is a pacing problem. Those 7 questions require actual calculation steps, and candidates who haven't practiced them under timed conditions often rush and make arithmetic errors that would not occur on paper.

Exam Quick Facts