Exam Cheat Sheet · Quick Reference
Idaho Plumbing Contractor Exam
Idaho · 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
100
Passing score
75%
Exam time
240 min
Administered by
PSI Services Contractor
Format
Reference materials allowed
Idaho State Portion 100 questions
2017 Idaho State Plumbing Code Chapter 2
1 Q · 1%
Drainage system terminology (building drain, building sewer, soil pipe, waste pipe, stack, branch, horizontal branch)Water supply and distribution terminology (building supply, water distribution pipe, riser, fixture branch, fixture supply, remote outlet)Backflow and cross-connection terminology (backflow, backsiphonage, backpressure backflow, cross-connection, critical level, air gap)Vent system terminology (dry vent, wet vent, continuous vent, stack vent, vent stack, branch vent, individual vent, relief vent, yoke vent)Trap and trap-related terminology (trap, trap seal, trap arm, trap primer, crown weir, top dip)Grease interceptor and special waste terminology (gravity grease interceptor, hydromechanical grease interceptor, FOG disposal system, grease removal device, interceptor/clarifier)Gray water and alternate water source terminology (gray water, reclaimed water, rainwater catchment system, on-site treated nonpotable water, mulch basin, surge tank)Pipe joint and connection type terminology (brazed joint, soldered joint, welded joint, flanged joint, flared joint, compression joint, heat-fusion weld joint, pressed fitting, push fit fitting)
2017 Idaho State Plumbing Code Chapter 5
5 Q · 5%
Permits and inspections for water heater installationWater heater location requirements (bedrooms, bathrooms, garages, attics)Temperature, pressure, and vacuum relief devices (TPR valves)Combustion air requirements (indoor, outdoor, mechanical, and combined methods)Venting system types and selection (Type B, Type L, single-wall metal pipe, direct-vent)Vent and chimney termination requirementsSizing of Category I venting systems using code tablesSeismic strapping, drainage pans, and physical installation requirements
2017 Idaho State Plumbing Code Chapter 6
5 Q · 5%
Cross-connection control and backflow prevention devices (air gap, AVB, PVB, SVB, DC, RP assemblies)Potable and nonpotable water system identification and labeling requirementsApproved pipe and fitting materials for water supply and distribution systemsJoining methods for water supply piping (soldered, brazed, flared, mechanical, solvent cement, heat-fusion)Water pressure regulation, pressure relief valves, and expansion tanksValve requirements and shutoff valve placement in water distribution systemsWater supply system sizing using fixture units and Table 610.4Residential fire sprinkler system installation, piping, and sizing requirements
2017 Idaho State Plumbing Code Chapter 7
2 Q · 2%
Drainage fixture unit (DFU) values and trap sizing by fixture typeSizing of drainage piping using maximum fixture unit loading and pipe length tablesApproved drainage piping materials and permitted locations (underground, aboveground, building sewer)Joints and connection methods by pipe material (ABS, PVC, cast-iron, copper, stainless steel, vitrified clay)Cleanout requirements: location, spacing, clearance, and accessGrade and slope requirements for horizontal drainage piping and building sewersDrainage of below-grade fixtures: backwater valves, sewage ejectors, sumps, and alarmsBuilding sewer requirements: materials, sizing, separation from water pipes, and testing
2017 Idaho State Plumbing Code Chapter 8
5 Q · 5%
Air gap and air break requirements for indirect waste connectionsIndirect waste piping sizing, length limits, and trapping requirementsIndirect waste receptors — standpipe dimensions, placement restrictions, and approval requirementsFood and beverage establishment indirect waste requirements (equipment types, pipe sizes, air gap mandates)Condensate waste disposal, pipe sizing, overflow protection, and point of dischargeChemical and industrial waste pretreatment, approved pipe materials, and venting restrictionsSteam and high-temperature discharge condensers, sumps, and blowoff pipe sizingClear water wastes, swimming pool drainage, cooling water, and pressure drainage connections
2017 Idaho State Plumbing Code Chapter 9
5 Q · 5%
Trap seal protection and siphonage/backpressure preventionVent pipe sizing based on fixture units and developed lengthVent pipe grades, connections, and rise requirementsVent termination requirements including roof clearance, frost/snow closure, and sidewall venting (Idaho-specific)Wet venting — vertical and horizontal bathroom group configurationsSpecial venting for island fixtures and air admittance valve (AAV) limitations (Idaho-specific)Circuit venting requirements and relief ventsCombination waste and vent systems — permitted conditions, sizing, and restrictions
2017 Idaho State Plumbing Code Chapter 10
3 Q · 3%
Trap requirements and where required (fixture trapping rules, tailpiece length, shared traps)Prohibited trap types (S-traps, bell traps, crown-vented traps, movable-part devices)Trap seal depth requirements (minimum and maximum liquid seal dimensions)Trap arm horizontal length limits and vent placement (Table 1002.2)Floor drain traps and trap seal protection (backwater valves, trap seal primers)Building traps (installation conditions, cleanouts, relieving vents)Grease interceptor requirements (hydromechanical vs. gravity types, sizing, maintenance, prohibited connections)Sand and oil/flammable liquid interceptor requirements (design, sizing, venting, special occupancy applications)
2017 Idaho State Plumbing Code Chapter 11
2 Q · 2%
Approved materials for storm drainage conductors, leaders, and underground pipingPrimary and secondary roof drainage system requirementsSizing of roof drains, vertical conductors, and leaders using rainfall tablesSizing of horizontal storm drains and sewers by projected roof and paved areaSubsoil drain installation, discharge, and sump requirementsControlled-flow roof drainage system design and conditionsTraps on storm drains and leaders connected to combined sewersTesting methods for storm drainage systems (water test and air test)
2017 Idaho State Plumbing Code Chapter 12
4 Q · 4%
Acceptable piping materials and joining methods (metallic pipe, tubing, plastic, CSST)Gas piping system sizing methods (longest length, branch length, hybrid pressure) and sizing tablesUnderground and aboveground gas piping installation requirementsGas pressure regulators: installation, venting, and overpressure protectionPressure testing and inspection procedures (test medium, test pressure, duration, leak detection)Appliance connections, shutoff valves, sediment traps, and flexible connectorsElectrical bonding and grounding requirements for gas piping systemsPurging requirements for gas piping systems
Plumbing sizing using schematics provided during exam
8 Q · 8%
Water supply fixture units (WSFU) and minimum fixture branch pipe sizes using Table 610.3Sizing water supply pipe and meter using Table 610.4 (pressure ranges, developed length, fixture unit totals)Drainage fixture unit (DFU) values and minimum trap/trap arm sizes using Table 702.1Maximum unit loading and maximum length of drainage and vent piping using Table 703.2Sizing vent piping based on fixture units and developed lengthSizing storm water drainage systems using rainfall rates and projected roof/paved areas (Tables 1101.8 and 1101.12)Flushometer valve fixture unit assignments for water supply sizing using Table 610.10Available pressure calculations for water supply sizing (elevation adjustments, pressure loss, developed length)
Contractor's Business and Law Reference Manual Section 1
1 Q · 1%
Purpose and components of a business planExecutive summary preparationManagement plan developmentMarketing plan elementsOperations plan considerationsFinancial plan and projected financial statementsSupporting documents assemblyBusiness research resources and tools
Contractor's Business and Law Reference Manual Section 2
1 Q · 1%
Selecting and working with a CPA or LPAAccountant fee structures and engagement lettersSelecting a business attorneyAttorney fee arrangements and referral servicesSelecting an insurance agent for contractor businessesKey questions when evaluating insurance coverage needsSelecting a bank for business needsComparing banking products, loan programs, and financial services
Contractor's Business and Law Reference Manual Section 3
1 Q · 1%
Sole proprietorship characteristics and owner liabilityGeneral partnership structure and assumed business name filing requirementsLimited liability partnership (LLP) formation and partner liability protectionsLimited partnership (LP) general vs. limited partner roles and filing requirementsLimited liability company (LLC) formation, naming rules, and registration with Idaho Secretary of StateCorporation types: S Corp, C Corp, and professional service corporation distinctionsForeign business entity registration requirements in IdahoSecurities regulations and Idaho Department of Finance notification requirements
Contractor's Business and Law Reference Manual Section 4
1 Q · 1%
DOPL mission and regulatory oversight roleSeven regulatory boards under DOPLLicensing requirements by trade category in IdahoPenalties for unlicensed workLicense qualification requirements and application processNon-refundable fees and supporting documentationDOPL contact information and application resources
Contractor's Business and Law Reference Manual Section 5
1 Q · 1%
Bookkeeping process and financial recordkeeping (journals, general ledger, trial balance)Financial statements (balance sheet, income statement, cash flow statement)Cash vs. accrual accounting methodsProject accounting methods (completed contract and percentage of completion)Financial ratios (liquidity, efficiency, leverage, and profitability ratios)Cash flow management and cash flow analysisEquipment depreciation methods (straight-line, MACRS, Section 179 deduction)Equipment acquisition options (leasing, renting, and purchasing)
Contractor's Business and Law Reference Manual Section 6
20 Q · 20%
Federal anti-discrimination laws (ADEA, ADA, Title VII, EPA, GINA, Pregnancy Discrimination Act)Reasonable accommodation and undue hardship under ADA and Title VIIWage and hour requirements under the Fair Labor Standards Act (FLSA)Family and Medical Leave Act (FMLA) eligibility and leave entitlementsFederal contractor labor law requirements (Davis-Bacon, Service Contract Act, Walsh-Healey, Copeland Anti-Kickback)Idaho-specific employment laws (minimum wage, wage payment, child labor, new hire reporting, recordkeeping)Required workplace poster obligations for employersEmployee Polygraph Protection Act and Consumer Credit Protection Act wage garnishment rules
Contractor's Business and Law Reference Manual Section 7
15 Q · 15%
Types of contractor insurance coverage (automobile, builder's risk, CGL, completed operations, pollution liability, EPLI, professional liability, property)Workers' compensation insurance requirements and employer obligations in IdahoUnemployment insurance employer liability and experience ratingSurety bonds: bid bonds, performance bonds, and payment bondsIndependent contractor classification criteria for UI tax exemptionMiller Act requirements for federal public works bondingUnemployment insurance reportable and non-reportable wagesPenalties for non-compliance with workers' compensation and unemployment insurance requirements
Contractor's Business and Law Reference Manual Section 8
3 Q · 3%
Open bids vs. closed bids in public works constructionBid decision factors (qualifications, schedule, cost, job site, risk)Plans and specifications components (general conditions, drawings, specifications)Estimation methods: conceptual, preliminary, and detailed estimatesQuantity survey/takeoff process and measurement unitsLabor, materials, and equipment pricing in detailed estimatesGeneral and project overhead costs and contingency/allowanceMarkup calculation and area modification factors
Contractor's Business and Law Reference Manual Section 9
1 Q · 1%
Essential elements of a valid contract (offer, acceptance, consideration, mutuality, legal purpose)Idaho Statute of Frauds — agreements required to be in writingIdaho construction contract retention limits and release timelines (Idaho Code 29-115)Types of construction contracts (lump sum, cost plus, time and materials, design-build, guaranteed maximum)Common required and optional provisions in construction contractsBreach of contract definition and civil remediesChange orders and additional work provisionsSubcontractor retention payment obligations and dispute withholding rules
Contractor's Business and Law Reference Manual Section 10
2 Q · 2%
Project management phases: initiation, planning, executing, monitoring/controlling, and closingScheduling methods: Critical Path Method (CPM) and Gantt chartsFloat/slack time and critical path identificationStaffing roles: owner's representative, construction manager, superintendent, foreman, and expediterCost control procedures: variance detection, diagnostics, and corrective actionInventory control and purchase order systems for materialsQuality control: conformance to design specifications during constructionProject closeout: project close and contract closure
Contractor's Business and Law Reference Manual Section 11
10 Q · 10%
OSHA employer responsibilities and general duty clauseOSHA recordkeeping requirements (Forms 300, 300-A, 301)OSHA worksite inspection procedures and prioritiesPersonal protective equipment requirements by hazard typeFall protection systems and height thresholdsHazard communication and material safety data sheetsOSHA cooperative and voluntary protection programs (VPP, SHARP, Alliance)Construction-specific safety standards (excavation, scaffolding, confined spaces)
Contractor's Business and Law Reference Manual Section 12
1 Q · 1%
Income tax filing requirements by business entity type (sole proprietor, partnership, S corporation, corporation, LLC)Federal and Idaho estimated tax payment requirements and thresholdsIdaho sales and use tax obligations for contractorsContractor vs. retailer vs. contractor/retailer sales tax classification and billing treatmentSales tax exemptions available to contractors (out-of-state jobs, agricultural irrigation, production machinery)Independent contractor vs. employee classification using the right-to-control testEmployment tax forms and withholding requirements for employees (W-4, I-9, W-2, EIN)Tax recordkeeping periods and retention requirements
Contractor's Business and Law Reference Manual Section 13
3 Q · 3%
Right to lien under Idaho Title 45 (who qualifies and for what work)Filing requirements and deadlines for lien claims (90-day rule, county recorder, required contents)Priority and ranking of mechanic's lien claims among competing lienholdersDuration and enforcement of mechanic's liens (6-month limitation, court proceedings)Release of mechanic's lien by posting surety bond (bond form, petition, hearing process)Contractor recovery and deduction of subcontractor debts in lien actionsResidential property disclosure requirements for general contractors (Idaho 45-525)Lien waivers and joint checks as protective measures for contractors
Key Distinctions
Accrual AccountingvsCash-Basis Accounting
Accrual accounting is GAAP-compliant and recognizes revenues and expenses when transactions occur, while cash-basis accounting records them only when payment is made or received and does not meet GAAP.
Contractor's Business and Law Reference Manual, Section 5: Accounting & FinanceNamed-Peril Builder's Risk InsurancevsAll-Risk Builder's Risk Insurance
Named-peril coverage protects only against losses from specifically listed items in the policy, while all-risk is the more common and broader coverage.
Section 7: Insurance – Builders Risk bullet, Page 65Experience Rate (UI Tax)vsCost Reimbursement (UI Tax)
Most employers are assigned an experience rate for Idaho unemployment insurance, while governmental units and 501(c)(3) nonprofits may elect to reimburse the Idaho Employment Security Fund directly for actual benefit payment costs.
Contractor's Business and Law Reference Manual, Section 7: Insurance — Cost Reimbursement EmployersBrazed JointvsSoldered Joint
A brazed joint uses alloys melting above 840°F (449°C) but below the melting point of the parts joined, while a soldered joint uses alloys that melt at or below 840°F (449°C).
2017 ISPC, Section 212.0 - Joint, BrazedContamination (High Hazard)vsPollution (Low Hazard)
Contamination creates an actual hazard to public health through poisoning or disease spread (High Hazard), while pollution impairs aesthetic qualities of potable water without creating a health hazard (Low Hazard).
2017 ISPC Section 218.0 (Pollution)AccessiblevsReadily Accessible
Accessible means access may first require removal of an access panel or similar obstruction, while Readily Accessible means direct access is available without removing any panel or obstruction.
2017 ISPC, Section 203.0Building DrainvsBuilding Sewer
The building drain is the lowest drainage piping inside the building that ends 2 feet outside the building wall, at which point the building sewer begins and conveys waste to a public sewer or disposal point.
2017 ISPC, Section 204.0 - Building DrainBattery of FixturesvsSoil Stack
A battery of fixtures is two or more similar adjacent fixtures discharging into a common horizontal waste or soil branch, while a soil stack is the common vertical pipe that receives discharge from those branches.
2017 ISPC Section 204.0Independent ContractorvsCovered Employee (Idaho UI)
An independent contractor must be free from the employer's direction and control over the manner, method, and mode of work; if the employer controls these factors, the worker is a covered employee subject to Idaho unemployment insurance tax.
Contractor's Business and Law Reference Manual, Section 7: Insurance — Independent ContractorTwo Permanent Openings Method (Combustion Air)vsOne Permanent Opening Method (Combustion Air)
The two-opening method requires each opening to have at least 1 sq in per 2,000 Btu/h for horizontal ducts, while the one-opening method requires at least 1 sq in per 3,000 Btu/h.
2017 ISPC Section 506.4.1(2)Scaffold Fall Protection ThresholdvsGeneral Walking/Working Surface Fall Protection Threshold
Scaffold fall protection is required when employees work more than 10 feet above a lower level, while the general fall protection threshold for other walking and working surfaces is 6 feet.
Contractor's Business and Law Reference Manual, Section 11 / Construction Industry Digest, Scaffolds sectionADA Undue Hardship StandardvsTitle VII Religious Accommodation Undue Hardship Standard
ADA undue hardship requires showing significant difficulty or expense to the employer (a higher bar), while Title VII's standard is met by showing more than a minimal burden.
Contractor's Business and Law Reference Manual, Section 6 — Americans with Disabilities Act (ADA), Disability Discrimination & Reasonable Accommodation & Undue HardshipKey Terms
Hot Water (2017 ISPC Section 210.0) 2017 ISPC, Section 210.0 - Hot Water
Water at a temperature of 120°F (49°C) or higher, as defined by the 2017 Idaho State Plumbing Code.
Confined Space — Fuel-Burning Appliances (2017 ISPC Section 205.0) 2017 ISPC Section 205.0 (Confined Space definition)
A room or space with a volume less than 50 cubic feet per 1,000 Btu/h of the aggregate input rating of all fuel-burning appliances installed there.
Gravity Grease Interceptor (2017 ISPC Section 209.0) 2017 ISPC, Section 209.0 - Gravity Grease Interceptor
A device identified by volume, 30-minute retention time, baffles, not fewer than two compartments, a total volume of at least 300 gallons (1,135 L), and gravity separation.
Horizontal Pipe (2017 ISPC Section 210.0) 2017 ISPC, Section 210.0 - Horizontal Pipe
A pipe or fitting installed in a horizontal position or making an angle of less than 45 degrees with the horizontal.
Cross-Connection (2017 ISPC Section 205.0) 2017 ISPC Section 205.0
A connection or arrangement, physical or otherwise, between a potable water supply and a plumbing fixture or device through which nonpotable substances could enter the potable system under any condition.
Bathroom Group (2017 ISPC Section 204.0) 2017 ISPC Section 204.0 (Bathroom Group definition)
Any combination of plumbing fixtures not exceeding one water closet, two lavatories, one bathtub or combination bath/shower, and one shower, and may include a bidet and an emergency floor drain.
Insanitary (2017 ISPC Section 211.0) 2017 ISPC Section 211.0 (Insanitary definition)
A condition including a trap that does not maintain a proper seal or a trap not protected against siphonage and backpressure by a vent pipe.
Battery of Fixtures (2017 ISPC Section 204.0) 2017 ISPC Section 204.0
A group of two or more similar, adjacent fixtures that discharge into a common horizontal waste or soil branch.
Vent Upsizing Rule (IPC 2021 Section 906.2) IPC 2021 — Section 906.2
An individual vent exceeding 40 feet in developed length must be increased one nominal pipe size for its entire length.
Minimum Individual Vent Size (IPC 2021 Section 906.2) IPC 2021 — Section 906.2
An individual vent may never be smaller than 1-1/4 inch, regardless of half the fixture drain size.
Static Water Pressure Conversion
Water exerts 0.433 psi per foot of elevation head; pressure difference between two points equals their elevation difference (in feet) multiplied by 0.433 psi/ft.
Drainage Fixture Unit (DFU) — UPC Table 702.1 UPC Chapter 7, Table 702.1 (Drainage Fixture Unit Values)
A measure of probable discharge load: flush-valve water closet = 6 DFU, lavatory = 1 DFU, floor drain = 2 DFU, service sink = 3 DFU.
Reduced-Pressure Principle (RP) Backflow Prevention (2017 ISPC Section 603.5.6.3) 2017 ISPC Section 603.5.6.3
Required on irrigation systems that include a chemical injector to protect the potable water supply.
Lead Content Limits — Solder/Flux vs. Fittings (2017 ISPC Section 604.2) 2017 ISPC Section 604.2
Solder and flux for potable water piping must contain no more than 0.2% lead; pipes, fittings, and fixtures must not exceed a weighted average of 0.25% lead on wetted surfaces.
Miller Act — Payment Bond Notification Contractor's Business and Law Reference Manual, Section 7: Insurance — The Miller Act
Under the Construction Industry Payment Protection Act amendment to the Miller Act, subcontractors may send payment bond claim notifications by any means verifiable by a third party, not solely by registered mail.
Safety and Health Management Systems (OSHA) Section 11, p. 99, Safety and Health Add Value
Workplaces that establish OSHA safety and health management systems can expect to reduce their injury and illness costs by 20 to 40 percent.
Formulas to Know
Static Water Pressure from Elevation Head
Pressure (psi) = Elevation head (ft) × 0.433 psi/ftElevation Head Required for a Given Pressure
Height (ft) = Desired pressure (psi) ÷ 0.433 psi/ftPressure Difference Between Two Fixtures
ΔP (psi) = (Elevation A − Elevation B) ft × 0.433 psi/ftTotal Drainage Fixture Units (DFU) for a Stack
Total DFU = Σ (fixture count × DFU rating per fixture type) for all floorsCombustion Air Volume — Standard Method
Required volume (ft³) = Total appliance input (Btu/h) ÷ 1,000 × 50 ft³Combustion Air Opening — Two Permanent Openings (Horizontal Duct)
Min free area each opening (in²) = Total input rating (Btu/h) ÷ 2,000Combustion Air Opening — One Permanent Opening
Min free area (in²) = Total input rating (Btu/h) ÷ 3,000Gas Pipe Spare Capacity
Spare capacity (cfh) = Pipe capacity from table (cfh) − Fixture demand (cfh)