Exam Cheat Sheet · Quick Reference

Oklahoma Residential Journeyman Plumbing and Natural Gas

Oklahoma  ·  PSI Services Contractor

Verified, not estimated. Every figure below is drawn from the official exam structure we maintain — question counts, passing standard and topic weighting. Practice questions are grounded in the source law with statute citations. We omit any figure we can't verify rather than guess at it.
Total questions
85
Passing score
75%
Exam time
180 min
Administered by
PSI Services Contractor
Format
Reference materials allowed

Oklahoma State Portion 85 questions

General Plumbing Knowledge and Regulations 8 Q · 9%
Calculate Area and VolumeGeneral Code RequirementsPlumbing DefinitionsNotches and Holes in Structural MembersTest SystemsWater ColumnPipe OffsetsPiping support requirements and spacing by material typeProtection of piping from physical damage, corrosion, and freezingTrenching, bedding, and backfilling requirementsPipe penetrations, waterproofing, and sealing of annular spacesMaterials identification, listing, and third-party certification +7 more
Piping, Valves, and Control Valves 8 Q · 9%
Piping ConnectionsCast Iron PipingCopper Piping and TubingSteel PipingPVC, CPVC, Plastic and PEX PipingValvesBackflow Prevention Devices and AssembliesWater Supply System Design and Pipe SizingPressure Requirements and Pressure-Reducing ValvesPipe Support Spacing and Installation RequirementsPipe Length Calculations and Fitting AllowancesDrainage Pipe Sizing and Slope Requirements +3 more
Fixtures and Equipment 10 Q · 12%
Fixture InstallationInstall Water HeatersRequirements for FixturesShower Compartment and Receptor RequirementsWater Closet and Flushing Device RequirementsFixture Trap Design and SizingBackflow Prevention Devices and ApplicationsTemperature and Pressure Relief Valves for Water HeatersWater Heater Location and Safety RequirementsBoiler Safety Controls and Operating RequirementsGas Appliance Installation and Clearance RequirementsFixture Standards and Material Requirements +4 more
Water Supply 10 Q · 12%
Water Supply and Distribution LinesProtection of Potable Water SupplyBackflowWater supply system pressure requirements and pressure-reducing valvesThermal expansion control and water hammer arrestorsPipe and tubing materials, joints, and connections for water service and distributionValves and shutoff requirements for water service and fixturesWater supply fixture units and pipe sizing methodsNonpotable water systems identification, storage, and distributionWater heater installation, relief valves, and safety requirementsDwelling unit fire sprinkler system water supply and pipe sizingWater service pipe separation from building sewer +7 more
Drains and Sewers 10 Q · 12%
Drain and Sewer PipeBuilding SewersSewer and Drain CleanoutsDFUsDrain and Water PipingDrainage pipe joints and connections by material typeHorizontal drainage piping slope requirementsDrain pipe sizing using fixture unit loads and tablesCleanout installation requirements and clearancesBackwater valvesSumps and sewage ejectorsDWV system testing procedures +7 more
Vents 7 Q · 8%
Vent InstallationWet VentingVent terminals and termination requirementsAir admittance valvesVent pipe sizing and developed lengthIndividual and common ventsCircuit ventingCombination waste and vent systemsWaste stack ventingIsland fixture ventingTrap seal protection and pressure differential limitsVent grades, connections, and drainage of condensate +6 more
Traps, Interceptors, Indirect, and Special Waste 5 Q · 6%
Ejector PumpsIndirect WasteTrapsTrap seal protection methods (primer valves and barrier devices)Prohibited trap typesTrap sizing requirements by fixture typeNumber of fixtures per trap and double-trapping prohibitionGrease interceptors and separatorsBackwater valvesSumps and ejector design requirementsTrap seal depth requirements (minimum and maximum liquid seal)Trap design and material construction standards +2 more
Isometric Analysis 13 Q · 15%
Isometric DrawingsFitting Allowances and Center-to-End CalculationsOffset, Diagonal, Rise, and Run Relationships45-Degree Offset Constants and Pipe Length CalculationsReading and Interpreting Venting System IsometricsEqual Spacing and Pipe Cut ListsParallel Offset CalculationsGrade, Drop, and Elevation in Plan View DiagramsRolling Offsets and True Offset CalculationsJumper Offsets Using 45° and 90° FittingsCombination Offsets (45° and 60° Fittings)Trigonometric Constants for Non-45° Offset Angles +3 more
Fuel Gas 4 Q · 5%
Gas Piping ConduitGeneral Gas Piping and ValvesPiping Supports and HangarsPipe SizingTestingInstallation and Joining Gas PipeThreadsCombustion air requirements and methodsAppliance location and clearances to combustiblesVenting systems and vent typesElectrical bonding of gas piping (CSST and metallic pipe)Appliance connectors and shutoff valves +11 more
Safety 10 Q · 12%
Construction ActivitiesLaddersFall Arrest SystemsPersonal Protective Equipment (PPE) selection, use, and employer responsibilitiesFire protection and prevention programsExcavation hazards and cave-in protective systemsFirst aid, medical services, and emergency responseHousekeeping and site sanitation requirementsHazardous substances and permissible exposure limitsEmployer safety training and accident prevention responsibilitiesGuardrail system specifications and load requirementsSafety net system installation, testing, and inspection +6 more

Key Distinctions

Atmospheric Vacuum Breaker Critical LevelvsPressure Vacuum Breaker Critical Level

Atmospheric vacuum breaker requires critical level not less than 6 inches above downstream piping/flood level rim, while pressure vacuum breaker requires not less than 12 inches.

IRC 2018, Section P2902.3.2, Page 632
Center-to-Center LengthvsEnd-to-End Length

Center-to-center lengths are equal for equal-spaced assemblies regardless of fitting type, but end-to-end lengths differ when different fitting types (e.g., 90° vs. 45° ell) are used because fitting allowances differ.

Mathematics For Plumbers And Pipefitters, Chapter 1 — Equal Spacing
Vertical Wet VentingvsHorizontal Wet Venting

Vertical wet venting runs the wet-vented section through a vertical stack, while horizontal wet venting runs it along a horizontal branch drain.

International Residential Code, Appendix N, Figure N4, Pages 896
Circuit VentvsIndividual Vent

A circuit vent is a single vent serving multiple fixtures on a horizontal branch drain, whereas an individual vent serves only one fixture.

International Residential Code, Appendix N, Figure N7, Page 898
Water Supply Lead Limit (general pipe and fittings)vsWater Supply Lead Limit (drinking/cooking pipe and fittings)

General water supply pipe and fittings may contain up to 8% lead, but pipe and fittings used for drinking or cooking water are restricted to a weighted average of 0.25% lead or less.

International Residential Code, Page 651, Section P2906.2
No-Hub Cast Iron Fitting Allowance (D measurement)vsThreaded Fitting Allowance

For No-Hub cast iron, the 'D' measurement (center-to-end of fitting to pipe coupling end) is used directly for fitting allowance calculation, while threaded fittings require an additional thread-in measurement to be subtracted.

Mathematics For Plumbers And Pipefitters, Cast Iron Assemblies with Various Bends section
45°/60° Combination Offset — Standard Positionvs45°/60° Combination Offset — Alternate Position

In the standard position, rise equals the offset and setback equals 1.414 × offset; in the alternate position, rise equals 1.414 × offset and setback equals the offset.

Mathematics For Plumbers And Pipefitters, Chapter 2 — Combination Offsets
Copper or Copper-Alloy Pipe Horizontal Support SpacingvsCopper Tubing (1¼ inch and smaller) Horizontal Support Spacing

Copper or copper-alloy pipe requires hangers at maximum 12-foot horizontal intervals, while copper tubing 1¼ inches and smaller requires support at maximum 6-foot horizontal intervals.

IRC Table P2605.1 / IPC Table 308.5
Water Service Pipe and Sewer in Same Trench — Approved Sewer MaterialvsWater Service Pipe and Sewer in Same Trench — Non-Approved Sewer Material

When the building sewer is constructed of approved materials (Table P3002.1(2)), standard separation applies; when NOT of approved materials, at least 5 feet of undisturbed or compacted earth horizontal separation is required.

IRC P2906.4.1 / IPC 603.2
Frostproof Hose BibbvsStandard Hose Bibb Subject to Freezing

A standard hose bibb subject to freezing requires an accessible stop-and-waste valve inside the building, but a frostproof hose bibb whose stem extends through building insulation into an open heated or semiconditioned space is exempt from this requirement.

IRC P2903.10
Parallel (Manifold) Distribution Line — ≤60 ft developed length, ≥40 psivsStandard Water Distribution Line Sizing

In a parallel manifold system where developed length is 60 feet or less and available pressure is at least 40 psi, individual distribution lines may be as small as ⅜ inch diameter, which is smaller than typical standard sizing requirements.

IRC P2903.8.2
Type C Soil ClassificationvsStable Rock (Excavation)

Excavations in Type C soil (e.g., submerged or freely seeping soil) always require a protective system when 5 feet or more deep, while excavations made entirely in stable rock are exempt from protective system requirements regardless of depth.

29 CFR 1926, Subpart P, §1926.652(a)(1) and Appendix A

Key Terms

NSF 61 Listing Requirement for Water Supply Piping International Residential Code, Page 622, Section P2609.5
Per IRC Section P2609.5, water service pipes, water distribution pipes, connecting fittings, control valves, faucets, and appurtenances used to dispense water intended for human ingestion must be evaluated and listed as conforming to NSF 61.
Lead Content Limit — General Water Supply Pipe and Fittings International Residential Code, Page 651, Section P2906.2
Per IRC P2906.2, pipe and fittings used in the water supply system shall contain not greater than 8 percent lead.
Prohibition on Underground Stop-and-Waste Valves International Residential Code, Page 638, Section P2903.9.5
Per IRC P2903.9.5, potable water outlets and combination stop-and-waste valves shall not be installed underground or below grade.
Main Shutoff Valve Requirement Per Dwelling Unit IRC P2903.9.1
Per IRC P2903.9.1, each dwelling unit must have an accessible, full-open type main shutoff valve with nominal restriction to flow and provision for drainage (bleed orifice or separate drain valve) near the water service entrance.
Cold-Water Shutoff Valve at Water Heater IRC P2903.9.2
Per IRC P2903.9.2, a readily accessible full-open valve must be installed on the cold-water supply pipe at or near each water heater to allow isolation for service.
Thermal Expansion Pressure Control Device IRC P2903.4.2
Per IRC P2903.4.2, when a backflow preventer, check valve, or similar device is installed on a system with storage water heating equipment, a device must be installed to control increased pressure caused by thermal expansion.
PVC Solvent-Cement Joint Requirements IRC P2906.9.1.4 / IPC 605.21.3
Per IRC P2906.9.1.4/IPC 605.21.3, PVC solvent-cemented joints in water supply piping require a purple primer conforming to ASTM F656 and solvent cement conforming to ASTM D2564 applied to all joint surfaces.
Underground Water Service Pipe Minimum Pressure Rating IRC P2906.4 / IPC 605.3
Per IRC P2906.4/IPC 605.3, water service pipe installed underground and outside a structure must have a working pressure rating of not less than 160 psi at 73°F.
Steel Shield Plate (Pipe Protection at Framing) IRC P2603.2.1 / IPC 305.6
Per IRC P2603.2.1/IPC 305.6, when piping (other than cast iron or galvanized steel) passes through a framing member and is less than 1¼ inches from the nearest edge, a steel shield plate of not less than 0.0575 inch (No. 16 gauge) thickness is required.
Circuit Vent International Residential Code, Appendix N, Figure N7, Page 898
A single vent that serves multiple fixtures connected along a horizontal branch drain, as illustrated in IRC Appendix N, Figure N7.
Isometric Drawing International Residential Code, Appendix N, Page 893
A three-dimensional style of drawing commonly used to illustrate residential plumbing venting methods, as referenced in IRC Appendix N.
Type C Soil 29 CFR 1926, Subpart P, §1926.652(a)(1) and Appendix A
Per 29 CFR 1926 Appendix A to Subpart P, submerged soil or soil from which water is freely seeping is classified as Type C — the least stable soil category — always requiring cave-in protection in excavations 5 feet or more deep.
Asbestos TWA Permissible Exposure Limit (PEL) 29 CFR 1926, Subpart Z, §1926.1101(c)(1) and (i)(1)
Per 29 CFR 1926.1101(c)(1), the 8-hour time-weighted average PEL for airborne asbestos on construction sites is 0.1 fiber per cubic centimeter of air.
Guardrail Top Rail Height 29 CFR 1926, §1926.502(b)(1)
Per 29 CFR 1926.502(b)(1), the top edge of a guardrail system must be 42 inches (plus or minus 3 inches) above the walking/working level.
Equivalent Noise Exposure Factor (Fe) 29 CFR 1926, §1926.52(d)(2)(ii)
Per 29 CFR 1926.52(d)(2)(ii), Fe is calculated as the sum of (time at each level / permissible time at that level) for all noise periods; if Fe exceeds 1, the combined daily noise exposure exceeds permissible limits.
Gas Appliance Front Clearance (Performance-Based) IRC G2409.4.5 (308.4.3)
Per IRC G2409.4.5 (308.4.3), front clearance for central-heating boilers and furnaces is not a fixed numerical dimension but must be sufficient to service the burner and the appliance.

Formulas to Know

End-to-End Pipe Length (Copper Fittings)E-E = Center-to-Center − (Fitting Allowance₁ + Fitting Allowance₂)
End-to-End Pipe Length (No-Hub Cast Iron)E-E = Center-to-Center − (D₁ + D₂) [where D = center-to-end of each fitting]
45°/60° Combination Offset — Alternate Position: RiseRise = 1.414 × Offset
45°/60° Combination Offset — Alternate Position: DiagonalDiagonal = 2 × Offset
45°/60° Combination Offset — Standard Position: SetbackSetback = 1.414 × Offset
Combined Noise Exposure FactorFe = (T₁/L₁) + (T₂/L₂) + … + (Tₙ/Lₙ) [Fe > 1 means overexposure]
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