Exam Cheat Sheet · Quick Reference
Oklahoma Plumbing Journeyman 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%
IPC Chapter 1 scope, intent, and applicability of the plumbing codePermit requirements, application procedures, and exempt workCode official duties, inspection authority, and enforcement powersRequired plumbing system tests and inspection typesPipe length calculations using fitting allowances for threaded, copper, and PVC fittingsOffset and diagonal calculations using angle constants (45°, 60°, other angles)Volume, pressure, and capacity calculations for water systemsPipe material types, weights, and schedules (standard, copper, plastic, cast iron)Head PressurePipe JointsSolvent Welded Pipe JointsCalculations of Area and Volume
+12 more
Piping, Valves, and Control Valves
8 Q · 9%
Pipe joints, fittings, and connection methods for gas and water pipingWater supply and distribution pipe materials, standards, and fittingsValves: types, required locations, and control valve functions (pressure-reducing, backflow preventers, relief valves)Pipe length calculations: fitting allowances, center-to-center and end-to-end measurementsPiping support, hangers, and spacing requirementsPVC Piping and ConnectionsCPVC Piping and ConnectionsGalvanized Piping and ConnectionsCopper Tubing and ConnectionsCopper Piping and ConnectionsPolyethylene Piping and ConnectionsPEX Piping and Connections
+5 more
Fixtures and Equipment
8 Q · 9%
Minimum number and type of plumbing fixtures by occupancy classificationFixture installation requirements (spacing, clearances, and setting)Individual fixture standards and waste outlet requirements (water closets, lavatories, showers, bathtubs, sinks, urinals)Flushing devices, shower valves, and temperature-limiting controls for fixturesWater heater installation, safety devices, and relief valve requirementsTrap requirements, prohibited trap types, and trap seal protectionInterceptors and separators (grease, oil, sand) installation and sizingGas appliance installation requirements (cooking appliances, water heaters, room heaters, clothes dryers)Identify Minimum Plumbing Needs for Structures/FacilitiesInstall Fixtures and Associated Equipment
Water Supply
10 Q · 12%
Backflow prevention devices, assemblies, and application requirementsWater distribution system design criteria including flow rates, pressures, and pipe sizingApproved piping materials, fittings, and joining methods for water service and distributionPotable water protection including cross-connection control and identification of nonpotable systemsValve requirements including full-open valves, shutoff valves, and pressure-reducing valvesWater pressure booster systems, water hammer arrestors, and thermal expansion controlHot water supply system requirements including temperature limits and recirculation systemsNonpotable water systems including graywater reuse and rainwater collection storage and distributionWater Supply and Distribution LinesProtection of Potable Water SupplyBackflow
Drains and Sewers
10 Q · 12%
Sanitary drainage pipe materials and standards (above-ground, underground, and building sewer)Drainage system sizing using fixture unit values and pipe sizing tablesSlope, installation, and fittings for horizontal drainage pipingCleanout requirements (location, spacing, size, and access)Sumps, ejectors, and below-grade drainage systemsBackwater valves and sewage backflow protectionStorm drainage system design and sizing (roof drains, conductors, leaders, and gutters)Indirect waste piping, air gaps, air breaks, and waste receptorsDrain and Sewer PipeBuilding SewersSewer and Drain CleanoutsSewage Ejectors and Sump Pumps
+3 more
Vents
13 Q · 15%
Vent pipe sizing and developed length (IPC stack vents, vent stacks, individual/branch/circuit vents)Vent terminal location and termination requirements (roof extension height, clearances from openings, wall terminations)Venting methods and types (individual, common, wet, circuit, combination waste-and-vent, single-stack, island fixture)Air admittance valves (installation, location, size, prohibited installations, required outdoor vent)Vent connections and grades (dry vent rise, connection above drain centerline, grade back to drainage)Vent InstallationDeveloped Length
Traps, Interceptors, Indirect, and Special Waste
5 Q · 6%
Fixture trap requirements, dimensions, and prohibited trap typesTrap seal depth, protection methods, and primer devicesGrease interceptors and automatic grease removal devicesOil separators and sand interceptors for commercial applicationsIndirect waste piping requirements and air gap vs. air break distinctionsWaste receptors, standpipes, and hub drain installationSpecial waste neutralization for corrosive waste dischargeInterceptor and separator venting, access, and maintenance requirementsTrapsInterceptors and SeparatorsIndirect and Special Waste
Isometric Analysis
7 Q · 8%
Calculating center-to-center (c-c) pipe lengths from isometric diagramsCalculating end-to-end (e-e) pipe lengths using fitting allowances45° offset constants (1.414 diagonal multiplier, 0.707 offset multiplier) applied to isometric layoutsThree-pipe offset diagrams with rise, run, and diagonal relationshipsFitting allowances for threaded, copper, PVC, and cast iron fittings in isometric assembliesSolving multi-fitting assemblies with wyes, tee-wyes, and elbows from isometric drawingsRolling offsets and true offset calculation using the Pythagorean theoremReading and interpreting offset terminology (offset, diagonal, rise, run, travel) from pipe diagramsIsometric Drawings
Fuel Gas
10 Q · 12%
Gas pipe sizing methods, tables, and equations (longest length, branch length, hybrid pressure)Approved piping materials and fittings (steel, copper, CSST, polyethylene, prohibited materials)Pressure requirements, allowable pressure drop, and maximum operating pressureVenting systems for fuel gas appliances (vent types, sizing, termination, connectors)Combustion air requirements for gas appliances (indoor, outdoor, mechanical methods)Appliance installation requirements (location, clearances, access, prohibited locations)Pipe testing, purging, identification, and leak checkingPipe length calculations and fitting allowances for fuel gas pipingGas Distribution Pipe SizingGas Pressure RegulatorsHangers and SupportsDirection Changes
+14 more
Safety
4 Q · 5%
Fall protection trigger heights and duty to provide fall protection (6-foot rule, specific work conditions)Personal fall arrest system components, specifications, and proper useGuardrail system requirements and specificationsLadder safety requirements, proper use, and inspectionPersonal protective equipment selection, provision, and maintenance (head, eye, face, foot, hearing protection)Safety net systems installation and inspection requirementsStairway construction requirements and stairrail/handrail specificationsFall protection training, certification, and retraining requirementsResponsibility for Providing Personal Protective EquipmentExcavation SafetyEmployee Protection in Trenches and ExcavationsSafety Training Requirements
+13 more
Key Distinctions
Air gap (indirect waste)vsAir break (indirect waste)
An air gap is measured between the indirect waste pipe and the flood level rim of the waste receptor, while an air break is provided between the indirect waste pipe and the trap seal of the waste receptor.
IPC 2018 Chapter 8 Indirect Special Waste, Section 802.3.2Equipment for food storage, preparation and handlingvsCommercial dishwashers, food utensil sinks, nonpotable clear-water waste
Food storage/preparation/handling equipment must discharge through an indirect waste by means of an air gap specifically, whereas dishwashers (802.1.6), food utensil sinks (802.1.7) and nonpotable clear-water waste (802.1.5) are permitted to use either an air gap or an air break.
IPC 2018 Chapter 8 Indirect Special Waste, Section 802.1.1Threaded pipe fitting allowancevsCopper/PVC fitting allowance
Threaded fittings deduct center-to-face minus the thread-in for each fitting, while copper and PVC fittings deduct only center-to-face minus the depth of the solder cup (or socket) with no thread-in calculation.
Mathematics for Plumbers and Pipefitters (8th ed.), Page 44No-Hub cast iron fitting allowancevsThreaded fitting allowance
For No-Hub cast iron the D dimension of each fitting is subtracted directly from center-to-center with no thread-in deduction (pipe joins with a shield and clamp), unlike threaded pipe where the thread-in is credited back.
Mathematics for Plumbers and Pipefitters (8th ed.), Pages 107-108 (Unit 28, Cast Iron Assemblies with Various Bends, Sample Problem 1)1.414 constant (45° offset)vs0.707 constant (45° offset)
1.414 × offset gives the diagonal (travel), while 0.707 is used for the reverse calculation of finding the offset from a known diagonal.
Mathematics for Plumbers and Pipefitters (8th ed.), Pages 67-68Cosecant of 60° (1.1547)vsCotangent of 60° (0.5774)
For a 60° offset the diagonal equals offset × 1.1547 (cosecant), while the run equals offset × 0.5774 (cotangent).
Mathematics for Plumbers and Pipefitters (8th ed.), Pages 95-96Fixture calculation for multiple occupanciesvsFixture calculation for a single occupancy
Per IPC 403.1.1, with multiple occupancies the fractional numbers for each occupancy are first summed and then rounded up to the next whole number, whereas single-occupancy calculations round each fractional number up individually.
IPC 2018 Section 403.1.1Urinal substitution in assembly and educational occupanciesvsUrinal substitution in all other occupancies
Urinals may replace up to 67 percent of required water closets in assembly and educational occupancies, but only 50 percent in all other occupancies.
IPC 2018 Section 424.2Separate-sex facilities exception — business occupancyvsSeparate-sex facilities exception — structure/tenant space
Separate facilities are not required in business occupancies with a maximum occupant load of 25 or fewer (Exception 4), while for structures or tenant spaces the exception applies at a total occupant load, employees plus customers, of 15 or fewer (Exception 2).
IPC 2018 Section 403.2Floor drain outlet (general)vsFloor drain in coin-operated laundry / multiple-family central washing room
General floor drains need an outlet not less than 2 inches in diameter, while rooms with automatic clothes washers in public coin-operated laundries and multiple-family central washing facilities require floor drains with an outlet not less than 3 inches.
IPC 2018 Section 413.3Plastic water closet floor flangevsCopper alloy water closet floor flange
Plastic floor flanges must be not less than 0.25 inch thick, while copper alloy flanges require a minimum of 0.125 inch.
IPC 2018 Section 405.4.1Wet ventvsCircuit vent / combination waste-and-vent
A wet vent carries the discharge of one fixture while venting others (classically a single bathroom group), whereas circuit vents serve batteries of fixtures and combination waste-and-vent is a different, more restricted system.
Vent stackvsStack vent
The vent stack is a separate vertical vent pipe connecting near the base of the soil stack to circulate air and rejoining the stack vent above the highest fixture; the stack vent is the extension of the soil stack itself.
IPC 2021 Section 202Temperature limit for shower/tub-shower valvesvsTemperature limits for bidets and tankless heaters
Shower and tub-shower combination valves must be limited to 120°F at the point of use, bidet fitting discharge is limited to 110°F, and tankless water heaters for domestic uses are limited to 140°F (which does not supersede protective shower valves).
IPC 2018 Section 412.3Key Terms
Air gap (Section 802.3.2 / 802.1.1) IPC 2018 Chapter 8 Indirect Special Waste, Section 802.3.2
The vertical separation measured between the indirect waste pipe and the flood level rim of the waste receptor, required specifically for equipment and fixtures used for storage, preparation and handling of food.
Air break (Section 802.3.2) IPC 2018 Chapter 8 Indirect Special Waste, Section 802.3.2
A separation provided between the indirect waste pipe and the trap seal of the waste receptor.
Branch interval (IPC 2021 Section 202) 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.
Wet vent
A pipe that vents one or more fixtures while also carrying the discharge of another fixture, the classic arrangement being a single bathroom group.
Vent stack (IPC 2021 Section 202) IPC 2021 Section 202
A separate vertical vent pipe installed to circulate air through the drainage system, connecting near the base of the soil stack and rejoining the stack vent above the highest fixture.
Crown vent prohibition (IPC 2021 Section 909.3) IPC 2021 Section 909.3
A vent shall not be installed within two pipe diameters of the trap weir, so a 1½" trap requires at least 3 in and a 2" trap at least 4 in from the weir to the vent connection.
Trap arm / maximum distance from trap to vent (IPC 2021 Table 909.1) IPC 2021 Table 909.1
The permitted developed length from trap weir to vent, limited to 6 ft for a 1½" trap and 8 ft for a 2" trap; water closets are self-siphoning fixtures whose distance is not limited.
Trap liquid seal (IPC 2018 Section 1002.4) IPC 2018 Section 1002.4
Each fixture trap shall have a liquid seal of not less than 2 inches and not more than 4 inches, or deeper for special designs relating to accessible fixtures.
Grease interceptor serving as a fixture trap (IPC 2018 Section 1002.1 Exception 3) IPC 2018 Section 1002.1 Exception 3
A grease interceptor is permitted to serve as the trap for a combination sink of not more than three compartments where the developed length of waste pipe from the most upstream fixture outlet to the interceptor inlet does not exceed 60 inches.
Fitting allowance Mathematics for Plumbers and Pipefitters (8th ed.), Page 44
The amount deducted from a center-to-center measurement for each fitting — center-to-face minus thread-in for threaded fittings, or center-to-face minus depth of the solder cup for copper (and the equivalent socket depth for PVC).
Set (offset terminology) Mathematics for Plumbers and Pipefitters (8th ed.), Review of Basic Fundamentals, Chapter 1, offset terminology section
A shortened form of "offset" meaning the perpendicular center-to-center distance between two parallel pipes; "travel"/"diagonal" is the connecting pipe and "run" is the horizontal component.
Vacuum relief valve (IPC 2018 Section 504.2) IPC 2018 Section 504.2
A valve complying with ANSI Z21.22 required on bottom-fed water heaters and bottom-fed tanks connected to water heaters, in addition to the temperature and pressure relief valve.
Temperature relief valve location (IPC 2018 Section 504.4.1) IPC 2018 Section 504.4.1
Temperature relief valves shall be located in the tank so as to be actuated by the water in the top 6 inches of the tank served.
Water pressure-reducing valve (UPC Section 604.8) UPC Section 604.8
Where building water pressure exceeds 80 psi static, an approved pressure-reducing valve conforming to ASSE 1003 or CSA B356 with strainer must reduce pressure to not greater than 80 psi static.
Water-hammer arrestor (UPC Section 604.9) UPC Section 604.9
A device conforming to ASSE 1010 that must be installed where quick-closing valves are utilized.
Pressure vacuum breaker assembly (UPC Section 608.14.5) UPC Section 608.14.5
A backflow assembly installed with its critical level not less than 12 inches above all downstream piping and outlets.
CSST bonding (2018 IFGC Section 310.2) IFGC 2018 Section 310.2
CSST gas piping not listed with an arc-resistant jacket or coating must be electrically continuous and bonded to the grounding electrode system of the electrical service.
Static (head) pressure
Pressure produced by vertical elevation of water only, equal to the vertical height of water above the point times 0.433 psi per foot; horizontal pipe length and tank width do not affect it.
Formulas to Know
End-to-end (cut) length of threaded pipe
e-e = c-c − total fitting allowance, where total allowance for two fittings = 2(A center-to-face) − 2(B thread-in); equivalently cut length = c-c − (takeoff × 2 fittings) + (thread engagement × 2 ends). Example: 42 − (2 × 2¼) + (2 × ½) = 38½"; 36 − (2 × 2) + (2 × ½) = 33.00 inCut length for soldered/solvent-cemented and No-Hub joints
e-e = c-c − sum of fitting allowances (no thread-in added back). PVC example: 10" − (⁹⁄₁₆ + ⁵⁄₁₆) = 9⅛"; No-Hub example: 65¹⁄₁₆ − (3 + 3) = 59¹⁄₁₆"; copper sweat example: 24 − (2 × ½) = 23.00 in45° offset relationships
travel (diagonal) = set × 1.414; set (offset) = travel × 0.707; run = set × 1.000 (run = offset = rise). Examples: 16 × 1.414 = 22.62 ≈ 22-5/8"; 20 × 1.414 = 28.28 ≈ 28-1/4"22½° and 60° offset travel/run
22½°: travel = set × 2.613 (10 × 2.613 = 26.13 ≈ 26-1/8"). 60°: diagonal = offset × 1.1547 (cosecant) and run = offset × 0.5774 (cotangent). Parallel 45° offsets: difference in length = 0.414 × spreadRolling offset true offset and travel
true offset = √(set² + roll²); then travel = true offset × angle constant. Examples: √(12² + 10.5²) = 15.95"; √(12² + 9²) = 15.0", travel at 45° = 15.0 × 1.414 = 21.2", travel at 60° = 15.0 × 1.155 = 17.3"Pythagorean theorem for right-triangle piping layouts
C² = A² + B², so A = √(C² − B²); e.g., √(25² − 15²) = √400 = 20 ft (a 3-4-5 ratio triangle × 5)Static pressure and head conversion
static pressure = vertical height of water × 0.433 psi/ft (46 × 0.433 ≈ 20 psi; 60 × 0.433 ≈ 26 psi); height = pressure ÷ 0.433 (30 ÷ 0.433 = 69.3 ft; 20 ÷ 0.433 = 46.2 ft)Drain fall, percent slope and invert elevation
total fall = grade × run (⅛ in/ft × 32 ft = 4 in; ¼ in/ft × 48 ft = 12 in = 1.00 ft); percent slope = (rise per foot ÷ 12) × 100 (0.25 ÷ 12 × 100 = 2.08%); downstream invert = upstream invert − total fall (100.00 − 1.00 = 99.00')Tank and pipe capacity in gallons
volume = π × r² × h (use radius = ½ diameter), then gallons = cubic feet × 7.48. Examples: π × 1.5² × 5 = 35.34 ft³ → 264 gal; π × 2² × 6 = 75.4 ft³ → 565 gal (half height 3 ft → 37.7 ft³ → 282 gal); 100 ft of 2" ID pipe: π × (1/12)² × 100 = 2.18 ft³ → 16.3 gal. Also 1 cubic foot = 1,728 cubic inchesIndividual vent and stack vent sizing
Individual vent = one-half the fixture drain size but never less than 1¼" (½ of 1½" = 0.75 → 1¼"; ½ of 2" = 1" → 1¼"; ½ of 3" = 1½"); if developed length exceeds 40 ft, increase one nominal size for the entire length (44 ft, 60 ft → 1½"). Stack vent: enter Table 906.1 with stack size and DFU and pick the smallest vent whose allowable developed length covers the actual lengthRequired fixture count from occupant load
Divide total occupant load in half for equal distribution, then divide by the Table 403.1 ratio; e.g., 240 ÷ 2 = 120 female occupants, nightclub ratio 1 per 40 → 120 ÷ 40 = 3 water closets. For multiple occupancies, sum the fractions first, then round up