Exam Cheat Sheet · Quick Reference

Tennessee CMC-A Mechanical Plumbing

Tennessee  ·  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
110
Passing score
73%
Exam time
295 min
Administered by
PSI Services Contractor
Format
Reference materials allowed

Tennessee State Portion 110 questions

General Knowledge and Math 14 Q · 13%
Arithmetic operations and formula solving for plumbing applicationsUnit conversions and measurement systems (English and metric)Geometric shapes, area, and volume calculationsPythagorean theorem and right triangle solutionsPipe offset, diagonal, rise, and run calculations using angle constantsWater pressure, head, and force calculationsIPC definitions and plumbing code terminologyIPC scope, permit requirements, and inspection procedures
General Requirements (not including Gas) - Administrative, Structural, Backflow, Materials and Supports, Joints and Connections, Storm Drains, Testing 10 Q · 9%
AdministrativeStructuralBackflowMaterials and SupportsJoints and ConnectionsStorm DrainsTesting
Water Supply and Distribution 10 Q · 9%
Potable water protection and cross-connection controlBackflow prevention devices and assembliesPipe materials, fittings, and joining methods for water service and distributionWater pressure requirements, pressure-reducing valves, and booster systemsHot water supply system requirements and thermal expansion controlWater piping system sizing using fixture units and segmented loss methodWater heater installation, safety devices, and relief valve discharge pipingWater volume, pressure, and capacity calculations
Fixtures, including Water Heaters 6 Q · 5%
Water HeatersMinimum number of required plumbing fixtures by occupancy classificationFixture installation requirements and clearancesFaucets and fixture fittings including shower valves and temperature limiting devicesSafety devices for water heaters including relief valves and discharge pipingWater heater installation requirements including access, location, and connectionsHot water supply system requirements including temperature limits and recirculationBackflow protection for plumbing fixtures and appliancesFixture-specific standards and waste outlet requirements
Drain, Waste, and Vent Systems, including Indirect and Special Waste 28 Q · 25%
Indirect WasteSpecial WasteDrainage fixture unit (DFU) values and system sizingHorizontal drainage pipe slope and installation requirementsCleanout placement, sizing, and access requirementsTrap requirements, prohibited trap types, and trap seal protectionVent types, sizing, and terminal requirementsGrease interceptors and other interceptors and separatorsSumps, ejectors, and below-grade drainage systemsPipe materials, fittings, and joint methods for drainage and vent systems
Traps, Cleanouts, and Interceptors 6 Q · 5%
TrapsCleanoutsInterceptorsProhibited trap typesTrap seal depth requirements and protection methodsGrease interceptor sizing and installation requirementsOil separator requirements and designCleanout spacing, sizing, and access requirementsSand and specialty interceptors (clothes washer, bottling, slaughterhouse)Venting and maintenance of interceptors and separators
Isometric Analysis 20 Q · 18%
Center-to-center and end-to-end pipe length calculationsFitting allowances for threaded, copper, PVC, and welded fittings45-degree offset calculations using diagonal and rise/run constantsOffset calculations for other fitting angles (60°, 22½°, 11¼°, 72°) using trigonometric constantsThree-pipe diagonal assembly layout and pipe length determinationRolling offsets and true offset calculationsParallel offset spacing and equal spacing calculationsReading and applying pipe fitting data tables from appendix references
Gas Appliances and Piping 12 Q · 11%
Gas AppliancesGas PipingGas piping materials and fittings (metallic pipe, copper tubing, CSST, polyethylene plastic)Pipe sizing methods (longest length, branch length, hybrid pressure)Pressure testing and leak checks of gas piping systemsCombustion air requirements for gas appliances (indoor, outdoor, and combination methods)Venting systems for gas appliances (vent types, connectors, termination, sizing)Appliance location, clearances, and installation requirementsSpecific gas appliance requirements (furnaces, unit heaters, unvented room heaters, clothes dryers, water heaters)
OSHA Safety 4 Q · 4%
Employer accident prevention responsibilities and safety programsPersonal protective equipment (PPE) selection, provision, and paymentFall protection systems — guardrails, safety nets, and personal fall arrestExcavation safety — cave-in protection, sloping, shoring, and competent person inspectionsConfined space entry procedures and permit-required confined spacesFire protection and prevention — extinguishers, flammable liquid storage, and fire prevention plansHazardous substances exposure limits and asbestos handling requirementsWelding and cutting — compressed gas cylinder handling and storage

Key Distinctions

Copper Fitting AllowancevsThreaded Fitting Allowance

Copper fitting allowance equals center-to-face minus solder cup depth with no thread-in deduction, whereas threaded fitting allowance requires an additional thread-in deduction.

Mathematics for Plumbers, Unit 10, Pages 56-57 (Allowances for Copper Fittings)
PVC Fitting AllowancevsThreaded Fitting Allowance

PVC allowance is measured center to the outside shoulder of the hub cup (same process as copper, no thread-in deduction), while threaded fittings require a thread-in deduction step.

Mathematics for Plumbers, Unit 12, Pages 60-61 (Allowance for Plastic Fittings)
Center-to-Center (C-C) LengthvsEnd-to-End Length

Equal spacing produces identical C-C lengths regardless of fitting type, but different fitting allowances cause end-to-end lengths to differ when fitting types vary.

Mathematics For Plumbers And Pipefitters, Chapter 1 — Equal Spacing
Stack Vent SizingvsIndividual Vent Sizing

Stack vent size is determined from IPC Table 906.1 using DFU load and developed length of the stack, while individual vent size is based on half the fixture drain diameter (minimum 1¼") and increased one nominal size if developed length exceeds 40 feet.

IPC 2021 — Table 906.1
Vent ≤ 40 ft Developed LengthvsVent > 40 ft Developed Length

A vent 40 feet or less requires no size adjustment, but a vent exceeding 40 feet in developed length must be increased one nominal pipe size for its entire length.

IPC 2021 — Section 906.2
Horizontal Stack Offset SizingvsVertical Stack Sizing

Horizontal stack offsets must be sized using the building drain table (IPC Table 710.1(1)), not the vertical stack table.

Ipc 2021, Section 710.1.1
Private Garage Appliance ClearancevsResidential Garage Water Heater Ignition Source Height

Gas-fired appliances in private garages require a minimum 6-foot clearance above the floor (IFGC 305.5), while water heater ignition sources in residential garages must be elevated at least 18 inches above the garage floor (IRC P2801.7).

International Fuel Gas Code 2021, Page 3-7 (Section 305.5)
50 ppm Chlorine Disinfectionvs200 ppm Chlorine Disinfection

A 50 ppm chlorine solution must be held in the system for 24 hours, whereas a 200 ppm solution only requires a 3-hour contact time before flushing.

IPC Section 610.1
Potable Water PipingvsNonpotable Water Distribution Piping

Nonpotable water piping must be purple in color and marked 'CAUTION: NONPOTABLE WATER – DO NOT DRINK,' while potable water piping has no such color or marking requirement.

International Plumbing Code 2021, Page 6-13, Section 608.9.2
Wet VentvsCircuit Vent

A wet vent vents one or more fixtures while simultaneously carrying discharge of another fixture (classic single bathroom group), whereas a circuit vent serves a battery of multiple fixtures.

Water Supply System Pressure TestvsAnnual Backflow Preventer Inspection

The water supply system must hold working pressure for not less than 15 minutes to prove tight (IPC 312.5), while backflow prevention assemblies must be tested at installation, after repairs, and at least annually to confirm they are operable (IPC 312.10.2).

International Plumbing Code 2021, Page 3-5, Section 312.5
Segmented Loss Method Fitting Factor (IPC Appendix E)vsSimplified Sizing Method Fitting Factor (IRC Appendix P / E104.1)

The segmented loss method adds 50% of developed length for fittings (IPC E103.3 / IRC AP103.3), while the simplified sizing method multiplies actual pipe length by a factor of 1.2 to compensate for fitting losses.

International Plumbing Code 2021, Page E-4 (Section E103.3, Step 6)

Key Terms

Individual Vent Size Increase (IPC Section 906.2) IPC 2021 — Section 906.2
Per IPC 2021 Section 906.2, any individual vent whose developed length exceeds 40 feet must be increased by one nominal pipe size for its entire developed length.
Vent Stack Connection Distance (IPC Section 904.4) IPC Section 904.4
Per IPC Section 904.4, where a vent stack connects to the building drain, the connection must be located downstream of the drainage stack and within a distance equal to 10 times the diameter of the drainage stack.
Horizontal Stack Offset Sizing (IPC Section 710.1.1) Ipc 2021, Section 710.1.1
Per IPC Section 710.1.1, horizontal stack offsets must be sized using the building drain criteria in Table 710.1(1), not the stack sizing table.
Hot Water Developed Length Limit (IPC Section 607.2) International Plumbing Code 2021, Page 6-11, Section 607.2
Per IPC Section 607.2, the developed length of hot or tempered water piping from the source to any fixture shall not exceed 50 feet.
Cleanout Interval (IPC Section 708.1.1) International Plumbing Code 2021, Page 7-7 (Section 708.1.1)
Per IPC Section 708.1.1, cleanouts on horizontal drainage pipes inside buildings must be located at intervals not exceeding 100 feet, measured along the developed length of the piping.
Cleanout at Change of Direction (IPC Section 708.1.4) International Plumbing Code 2021, Page 7-7 (Section 708.1.4)
Per IPC Section 708.1.4, a cleanout is required wherever a horizontal drainage pipe has a change of horizontal direction greater than 45 degrees.
Nonpotable Pipe Color and Marking (IPC Section 608.9.2) International Plumbing Code 2021, Page 6-13, Section 608.9.2
Per IPC Section 608.9.2, nonpotable water distribution piping must be purple and marked 'CAUTION: NONPOTABLE WATER – DO NOT DRINK,' with identification tape at least 3 inches wide fastened every 10 feet.
Pipe-Applied Vacuum Breaker Height (IPC Section 608.16.4) International Plumbing Code 2021, Page 6-15, Section 608.16.4
Per IPC Section 608.16.4, pipe-applied vacuum breakers must be installed not less than 6 inches above the flood level rim of the fixture or device served.
Minimum Slope for 4-inch Drainage Pipe (IPC Table 704.1) International Plumbing Code 2021, Page 7-3 (Table 704.1)
Per IPC Table 704.1, horizontal drainage pipes sized 3–6 inches require a minimum slope of 1/8 inch per foot; pipes 2½ inches or less require 1/4 inch per foot.
Developed Length International Plumbing Code 2021, Page 2-3
The length of a pipeline measured along the centerline of the pipe and all fittings, following the actual path of the pipe rather than straight-line distance.
Effective Opening International Plumbing Code 2021, Page 2-3
The minimum cross-sectional area at the point of water supply discharge, expressed as the diameter of a circle of equivalent area; for faucets, measured at the smallest orifice in the fitting body or supply piping.
Wet Vent
A pipe that simultaneously serves as the vent for one or more fixtures while also carrying the waste discharge of another fixture, as in a single bathroom group.
Static Pressure Conversion
Water exerts approximately 0.433 psi of static pressure per foot of vertical elevation head; pressure at a point equals the vertical height of water above it multiplied by 0.433.
Water Supply System Pressure Test Duration (IPC Section 312.5) International Plumbing Code 2021, Page 3-5, Section 312.5
Per IPC Section 312.5, the water supply system must be tested at not less than working pressure and that pressure held for not less than 15 minutes (not 30 minutes) to prove the system tight.
Lead-Free Solder Composition (IPC Section 605.12.3) International Plumbing Code 2021, Page 6-7 (Section 605.12.3)
Per IPC Section 605.12.3, solder used on water supply piping must be 'lead-free,' defined as a chemical composition of 0.2-percent lead or less.
Prohibited Joints – Saddle-Type Fittings (IPC Section 605.9) International Plumbing Code 2021, Page 6-6, Section 605.9
Per IPC Section 605.9, saddle-type fittings are specifically prohibited from use in water supply systems.

Formulas to Know

Static Water Pressure from Elevation HeadPressure (psi) = Elevation head (ft) × 0.433 psi/ft
Elevation Head Required for Target PressureHeight (ft) = Desired pressure (psi) ÷ 0.433 psi/ft
Pressure Difference Between Two FixturesΔP (psi) = (Elevation A − Elevation B) ft × 0.433 psi/ft
Equivalent Length of Run – Segmented Loss Method (50% rule)Equivalent length = Developed length × 1.50
Equivalent Length of Run – Simplified Sizing Method (1.2 factor)Equivalent length = Actual pipe length × 1.20
Minimum Vent Size Base (Individual Vent)Base vent size = max(1¼", ½ × fixture drain diameter); increase one nominal size if developed length > 40 ft
Pipe End-to-End Length from Center-to-CenterEnd-to-end = Center-to-center − fitting allowance (each end); fitting allowance = center-to-face − solder cup depth (copper/PVC) or center-to-face − thread-in (threaded)
Minimum Horizontal Drain Slope CheckRequired drop = pipe length (ft) × slope (in/ft); e.g., 4" pipe: drop = L × 1/8"
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