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
10 Q · 12%
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
8 Q · 9%
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
13 Q · 15%
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
7 Q · 8%
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
10 Q · 12%
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
4 Q · 5%
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-type vacuum breakervsPressure vacuum breaker assembly
An atmospheric vacuum breaker's critical level must be set not less than 6 inches above the highest downstream piping and the flood level rim, while a pressure vacuum breaker assembly requires not less than 12 inches (IRC 2024 P2902.3.2).
IRC 2024 Section P2902.3.2Wet ventvsCircuit vent
A wet vent is a pipe that carries the discharge of one fixture while venting others in the same bathroom group, whereas a circuit vent is a single vent serving multiple fixtures (a battery) connected on a horizontal branch drain.
IRC 2018 Appendix N, Figure N7Vertical wet ventingvsHorizontal wet venting
In vertical wet venting (IRC Appendix N, Figure N4-A) the wet-vented section runs vertically through the stack, while in horizontal wet venting (Figure N4-B / N3) the wet-vented section runs horizontally along the branch drain.
IRC 2018 Appendix N, Figure N4Center-to-center lengthvsEnd-to-end (cut) length
Equal spacing makes center-to-center lengths equal, but end-to-end lengths differ whenever the assemblies use different fittings (e.g., 90° ell vs. 45° ell) because the fitting allowances differ.
Mathematics for Plumbers and Pipefitters (8th ed.), Chapter 1 — Equal SpacingCopper (sweat) fitting allowancesvsThreaded fitting allowances
Copper end-to-end length is simply center-to-center minus the fitting allowances, while threaded fittings require the extra step of adding back the thread-in (thread engagement) at each end.
Mathematics for Plumbers and Pipefitters (8th ed.), Allowances for Copper Fittings sectionNo-Hub cast iron fitting allowance ("D")vsThreaded fitting allowance
The No-Hub "D" is the center-to-end distance used directly (subtract the D values from the center-to-center measurement), while threaded fittings require thread-in calculations.
Mathematics for Plumbers and Pipefitters (8th ed.), Cast Iron Assemblies with Various Bends section45°/60° combination offset — standard positionvs45°/60° combination offset — alternate position
Standard: rise = offset, setback = 1.414 × offset, diagonal = 2 × offset; alternate: rise = 1.414 × offset, setback = offset, diagonal = 2 × offset.
Mathematics for Plumbers and Pipefitters (8th ed.), Chapter 2 — Combination OffsetsRisevsRun
In a pipe offset the distance between two parallel vertical pipes is called the rise, while the same dimension between two parallel horizontal pipes is called the run ('set' is a shortened form of 'offset').
Mathematics for Plumbers and Pipefitters (8th ed.), Chapter 2 — Offset, Diagonal, Rise, and Run8 percent maximum lead in water supply pipe and fittingsvs0.25 percent weighted average for drinking/cooking supply and 0.2 percent for solders and fluxes
IRC P2906.2 caps lead in water supply pipe and fittings at 8 percent, but P2906.2.1 limits pipe and fittings supplying water for drinking or cooking to a 0.25 percent weighted average, and P2906.15 limits potable-water solders and fluxes to 0.2 percent.
IRC 2018 Section P2906.2Supply fittingvsWaste fitting
Per IRC R202 a fixture fitting is classified as either a supply fitting — one that controls the volume and/or directional flow of water and is attached to or accessed from a fixture or used with open/atmospheric discharge — or a waste fitting.
IRC 2024 Section R202Flush tank water closet supply pressurevsFlushometer valve and blowout fixture supply pressure
Per IRC Appendix P AP103.1, flush tank supplies need not less than 8 psi flowing at the highest fixture, while flushometer valves require 15 psi and blowout action fixtures require 25 psi.
IRC 2018 Section AP103.1Elevation to pipe centerlinevsElevation to pipe invert
Most piping is measured to the centerline, but sewers and house drains in plan view show elevations taken at the invert (inside bottom) of the pipe because it is a solid, verifiable surface.
Mathematics for Plumbers and Pipefitters (8th ed.), Chapter 2 — Elevation in a Plan View Pipe DiagramCopper/copper-alloy pipe hanger spacingvsCopper tubing 1¼ inch and smaller
Per IRC Table P2605.1 / IPC Table 308.5, copper or copper-alloy pipe is supported at maximum 12-foot horizontal intervals, while copper tubing 1¼ inches and smaller has a 6-foot maximum horizontal spacing.
IRC 2018 Table P2605.1 / IPC Table 308.5Key Terms
Branch interval IPC 2021 Section 202 (Branch interval)
A vertical length of stack of 8 feet or more between the connections of horizontal branches; branches connecting less than 8 feet apart fall within the same branch interval (IPC 2021 Section 202).
Developed length IRC 2024 Chapter 2
The length of a pipeline measured along the center line of the pipe and fittings (IRC 2024 R202).
Trap seal IRC 2024 Chapter 2
The maximum vertical depth of liquid that a trap will retain, measured between the crown weir and the top of the dip of the trap (IRC 2024 R202).
Bathroom group IRC 2024 Section R202
A group of fixtures, including or excluding a bidet, consisting of a water closet, lavatory, and bathtub or shower, located together on the same floor level (IRC 2024 R202).
Plumbing fixture IRC 2024 Section R202
A receptacle or device connected to a water supply system or discharging to a drainage system or both, that requires a supply of water and/or discharges liquid or liquid-borne solid waste (IRC 2024 R202).
Slip joint IRC 2024 Section R202
A mechanical-type joint used primarily on fixture traps in which tightness is obtained by compressing a friction-type washer (rubber, nylon, neoprene, lead or special packing) against the pipe by tightening a slip nut (IRC 2024 R202).
Vacuum breaker IRC 2024 Section R202
A device that prevents backsiphonage of water by admitting atmospheric pressure through ports to the discharge side of the device (IRC 2024 R202).
Temperature- and Pressure-Relief (T and P) valve IRC 2024 Section R202
A combination relief valve designed to function as both a temperature-relief valve and a pressure-relief valve (IRC 2024 R202).
Direct-vent appliance IRC 2024 Section R202
A fuel-burning appliance with a sealed combustion system that draws all air for combustion from the outside atmosphere and discharges all flue gases to the outside atmosphere (IRC 2024 R202).
Combustion air IRC 2024 Section R202
The air provided to fuel-burning equipment including air for fuel combustion, draft hood dilution, and ventilation of the equipment enclosure (IRC 2024 R202).
Steam heating boiler IRC 2024 Section G2403
A boiler in which steam is generated and that operates at a steam pressure not exceeding 15 psig (IRC 2024 G2403).
Invert Mathematics for Plumbers and Pipefitters (8th ed.), Chapter 2 — Elevation in a Plan View Pipe Diagram
The inside bottom of a pipe; elevations for sewers and house drains in plan view are measured to the invert.
Isometric drawing IRC 2018 Appendix N
The diagram type commonly used to illustrate residential plumbing venting methods; IRC Appendix N illustrates a variety of venting methods with isometrics.
Steel shield plate (concealed piping protection) IRC 2018 Section P2603.2.1 / IPC 305.6
A plate of not less than 0.0575 inch (No. 16 gauge) thickness required where piping other than cast iron or galvanized steel passes through a hole or notch less than 1¼ inches from the nearest edge of a stud, joist, rafter or similar member (IRC P2603.2.1 / IPC 305.6).
NSF 61 IRC 2018 Section P2609.5
The standard to which water service pipes, water distribution pipes, and the necessary connecting pipes, fittings, control valves, faucets and appurtenances dispensing water intended for human ingestion must be evaluated and listed (IRC P2609.5).
Vent rough-in for future fixtures IRC 2024 Section P3104.6
Where drainage piping is roughed in for future fixtures, the vent rough-in connection shall be not less than one-half the diameter of the drain and must be identified as a vent (IRC 2024 P3104.6).
Formulas to Know
Static (head) pressure and required height of water column
Static pressure (psi) = vertical height of water above the point (ft) × 0.433 psi/ft; Height (ft) = pressure (psi) ÷ 0.433. Between two fixtures, pressure difference = elevation difference × 0.433 (tank height does not matter).Fall (drop) of a graded horizontal drain
Total fall = horizontal run (ft) × grade (in./ft); e.g., 32 ft × 1/8 in./ft = 4 in.; 48 ft × 1/4 in./ft = 12 in. = 1.00 ft. For multiple runs, add each run's fall.Grade expressed as percent slope
Percent slope = (rise in inches per foot ÷ 12 in./ft) × 100; e.g., 1/4 in./ft → (0.25 ÷ 12) × 100 = 2.08%.Downstream invert elevation
Downstream invert = upstream invert − total fall; e.g., 100.00' − (48 ft × 1/4 in./ft = 1.00 ft) = 99.00'.Cut length of threaded pipe
Cut length = center-to-center − (fitting takeoff × 2 fittings) + (thread engagement × 2 ends); e.g., 42 − (2 × 2¼) + (2 × ½) = 38½ in.; 36 − (2 × 2) + (2 × ½) = 33.00 in.End-to-end (cut) length for copper/sweat or No-Hub fittings
End-to-end = center-to-center − total fitting allowances (no thread-in step); e.g., 10 − (½ + ¼) = 9¼ in.; 24 − (2 × ½) = 23.00 in. For No-Hub cast iron, subtract the center-to-end 'D' values from the center-to-center measurement.Offset travel and run from the set (simple offset constants)
Travel = set × constant: 45° → 1.414, 22½° → 2.613, 60° → 1.155. For a 45° offset, run = set × 1.000 (run equals set).Rolling offset — true offset then travel
True offset = √(set² + roll²); e.g., √(12² + 9²) = 15.0 in. Then travel = true offset × fitting constant (45° = 1.414 → 21.2 in.; 60° = 1.155 → 17.3 in.).Capacity in gallons of a tank or length of pipe
Volume (cu ft) = π × r² × height/length (in feet), then gallons = cu ft × 7.48; e.g., 3 ft dia. × 5 ft tall = 35.34 cu ft → 264 gal; 100 ft of 2-in. ID pipe = 2.18 cu ft → 16.3 gal.Minimum size of an individual (fixture) vent
Base size = one-half the diameter of the fixture drain, but never smaller than 1¼ in.; if the vent's developed length exceeds 40 ft, increase one nominal pipe size for its entire length (IPC 2021 Section 906.2). Examples: 1½ in. drain → 0.75 → 1¼ in. (1½ in. if over 40 ft); 2 in. drain → 1 in. → 1¼ in. (1½ in. if over 40 ft); 3 in. drain → 1½ in.