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Oklahoma Residential Journeyman Plumbing and Natural Gas — Practice Exam

What This Practice Exam Covers

The Oklahoma Residential Journeyman Plumbing and Natural Gas licensing exam is 85 questions delivered in 180 minutes, with a passing score of 75% (64 correct). The exam spans 10 topic areas drawn from the International Residential Code and OSHA construction safety standards.

This practice exam is available in two formats. The free practice exam gives you 10 questions per attempt pulled from a limited pool. You can retake it as many times as you like — it's a solid way to get a feel for question style and phrasing before committing to full prep.

The full practice exam mirrors the real test: 85 questions, a 180-minute timer, and questions drawn from a pool of 372+ items, so every attempt produces a different set. No two practice sessions look the same. Questions are built directly from the official topic list provided by the testing authority, so what you practice is exactly what the real exam tests.

What You'll Be Tested On

General Plumbing Knowledge and Regulations — 8 items
Expect area and volume calculations (cylinders, rectangular tanks), along with definitions pulled directly from IRC Section R202. Questions also cover notching and boring rules for structural members, pressure testing procedures, and water column measurements. Know the difference between air tests and water tests, and be comfortable converting pressure between psi and inches of water column.

Piping, Valves, and Control Valves — 8 items
You need to know joining methods for each pipe material: cast iron (hub-and-spigot, hubless), copper (soldered, press-fit), steel (threaded), and plastic (solvent-welded PVC/CPVC, PEX crimp and clamp). Questions distinguish where each material is code-permitted and what valves — gate, ball, globe, check — are required in specific situations.

Fixtures and Equipment — 10 items
This is one of the heavier sections. Topics include installation requirements for water closets and flushing devices, shower compartment dimensions and receptor slopes, water heater installation rules (pressure-relief valves, expansion tanks, seismic strapping), and fixture trap design. Per IRC Page 26, definitions like "vacuum breaker" appear directly as exam questions — know your Section R202 terms cold. Table P3201.7 governs trap sizing by fixture type.

Water Supply — 10 items
Covers potable water protection, backflow prevention devices (atmospheric vacuum breakers, pressure vacuum breakers, reduced-pressure principle assemblies), pressure-reducing valves, thermal expansion control, and water hammer arrestors. IRC Section P2904.5.2 governs fire sprinkler system supply duration — expect a calculation. Know the minimum and maximum static pressures and which devices apply to each backflow risk category under IRC Section P2902.

Drains and Sewers — 10 items
Drain fixture unit (DFU) values, building sewer sizing, cleanout placement and spacing, drain pipe slope requirements, and material-specific joint types. Know Table P3004.1 for drain pipe sizing. Questions test when a cleanout is required and where it must be located, plus DFU loading for common fixtures.

Vents — 7 items
Vent terminal heights above roof and clearances from openings (IRC Section P3103.1.1 and P3103.2), air admittance valve installation rules (Section P3114.4 and P3114.7), wet vent sizing and length limits, individual and common vent configurations, and developed vent length calculations. IRC Sections P3104.2 through P3104.6 govern common and individual vents — understand which fixtures qualify and at what pipe sizes.

Traps, Interceptors, Indirect, and Special Waste — 5 items
Know the prohibited trap types (S-traps, crown-vented traps, bell traps), trap seal depth requirements (2-inch minimum, 4-inch maximum under IRC Section P3201.2), trap sizing by fixture type per Table P3201.7, indirect waste receptor requirements, and trap seal protection through primer valves and barrier devices. Ejector pump applications and grease interceptor rules round out this section.

Isometric Analysis — 13 items
This is the single largest topic area and the one most candidates underestimate. You must read and interpret isometric plumbing drawings (IRC Appendix N, Figures N1–N7), calculate pipe cut lengths using fitting allowances for threaded, copper, plastic, and cast iron fittings, solve 45-degree offset problems using the 0.707 constant, calculate rolling offsets, equal spacing between parallel pipes, and interpret venting system isometrics. Source material is Mathematics for Plumbers and Pipefitters — you should be able to work multi-step offset and cut-list problems without a diagram in front of you.

Fuel Gas — 4 items
Gas piping material, joining methods, support spacing, prohibited locations, pressure testing, and pipe sizing. Know when a sediment trap is required, where gas shutoff valves must be installed (IRC Section G2420.5.1), and the rules for gas piping inside conduit. IRC Section G2406.2 governs prohibited locations.

Safety — 10 items
Pure OSHA — 29 CFR 1926 throughout. Topics include fall arrest systems (§1926.502), excavation and cave-in protective systems (§1926.652), ladder safety (§1926.1053), PPE selection, fire protection, and asbestos requirements (§1926.1101). Questions are very specific: guardrail heights, personal fall arrest system deceleration distances, and excavation protective system selection criteria all appear verbatim from the CFR.

Worked Sample Questions

Question 1 — Isometric Analysis

On an isometric drawing illustrating waste stack venting for a residential laundry area, which fixtures are typically grouped together on the circuit-vented branch?

• A. Bathtub and bidet only
• B. Two water closets and a shower
• C. Kitchen group, clothes washer standpipe, and laundry tub
• D. Three lavatories in series

Correct Answer: C

IRC Appendix N, Figures N6 and N7 show the standard isometric layout for waste stack venting. In those figures, the circuit-vented branch serving the laundry area groups the kitchen sink group, the clothes washer standpipe, and the laundry tub together — not bathroom fixtures. This question tests whether you can read a real isometric layout, not just recall a rule. The answer lives in the drawing itself.
Source: International Residential Code, Appendix N, Figures N6–N7, Page 898

Question 2 — Fixtures and Equipment

A device that prevents backsiphonage of water by admitting atmospheric pressure through ports to the discharge side of the device is known as a:

• A. Pressure-relief valve
• B. Backwater valve
• C. Air admittance valve
• D. Vacuum breaker

Correct Answer: D

IRC Section R202 defines a vacuum breaker as a device that prevents backsiphonage by admitting atmospheric air through ports on the discharge side. Each distractor describes a real device doing a different job: a backwater valve blocks sewage backflow, a pressure-relief valve releases excess system pressure, and an air admittance valve admits air into the drainage system (not the supply side). The exam regularly tests whether you can match the precise definition to the precise device.
Source: International Residential Code, Page 26 (Section R202 Definitions — Vacuum Breaker)

Question 3 — Water Supply

A residence is equipped with a dwelling unit fire sprinkler system. What is the minimum required water supply duration for a two-story home that is 2,200 square feet?

• A. 5 minutes
• B. 10 minutes
• C. 15 minutes
• D. 7 minutes

Correct Answer: B

IRC Section P2904.5.2 sets the supply duration at 10 minutes for dwelling units that are either two or more stories in height or have a floor area of 2,000 square feet or more. This home triggers both conditions. The 7- and 5-minute options are not code values; 15 minutes applies to larger commercial systems. Read the threshold carefully: 2,000 sq ft (not 2,500), and two stories (not three).
Source: IRC 2018, Section P2904.5.2

How to Read Your Score

The passing threshold is 75% — 64 correct out of 85. On the full practice exam, treat your first score as a diagnostic, not a verdict. Most candidates score below passing on attempt one, and that's useful information, not a reason to stop.

Look at your results by topic. Isometric Analysis carries 13 items — the most of any section. A weak score there can cost you the exam by itself, even if you're solid everywhere else. Safety (10 items), Water Supply (10 items), Drains and Sewers (10 items), and Fixtures and Equipment (10 items) are the next most consequential.

A practice score between 60% and 70% means you have identifiable gaps to close but are in range. A score below 60% means more foundational review is needed, particularly in the math-heavy sections. Scoring at exactly 75% on practice is not comfortable margin — exam-day pressure, unfamiliar phrasing, and time constraints all tend to push scores down. Aim for consistent scores of 80% or better before sitting for the real exam.

Retake the full practice exam after targeted study. The 372+ question pool ensures you'll see new questions each time, so repeat attempts continue building your exposure.

Where Candidates Lose Points

Isometric math errors are the leading source of lost points. The 45-degree offset constant (0.707) must be applied correctly — confusing which dimension is the offset versus the diagonal adds up fast across 13 questions. Fitting allowances differ by material, and skipping that step gives a wrong cut length even when the geometry is right. Practice full multi-step problems, not just the formula.

Definition confusion hurts on Fixtures and Vents. The IRC uses precise language — "vacuum breaker," "trap seal," "developed length," "wet vent" — and wrong-answer options are always plausible-sounding real devices. Learn the Section R202 definitions specifically.

Wrong code section for the right concept is common in Water Supply and Vents. Knowing backflow prevention exists isn't enough — you need to know which device applies to which risk level, and what the IRC says about installation height and location.

Safety section underpreparation is a pattern. Candidates focused on plumbing content sometimes treat the 10 OSHA questions as an afterthought. Questions from 29 CFR 1926 Subpart M (fall protection), Subpart P (excavation), and Subpart Z (asbestos) are specific — exact heights, distances, and trigger conditions, not general principles.

Time management becomes critical when isometric problems require multiple calculation steps. Budget your time so the math sections don't run you out of time on the code questions.

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