Tennessee CMC-A Mechanical Plumbing

14 questions | 13% of exam

Key Concepts

Arithmetic & Formula Solving - Solve for any unknown variable by isolating it (inverse operations). If A = π × r², then r = √(A/π). - Order of operations: Parentheses → Exponents → Multiply/Divide → Add/Subtract (PEMDAS). - Fractions in plumbing: Convert mixed numbers before multiplying (e.g., 2½ = 2.5).

Unit Conversions (English & Metric) - 1 foot = 12 inches | 1 yard = 3 feet | 1 mile = 5,280 feet - 1 gallon = 231 cubic inches | 1 cubic foot = 7.48 gallons - 1 meter = 3.281 feet | 1 inch = 25.4 mm | 1 liter = 0.2642 gallons - 1 psi = 2.31 feet of water head | 1 foot of head = 0.433 psi

Key Concepts

Administrative (IPC Chapter 1)

• Conflicts between requirements: Specific requirements govern over general; where sections conflict, the most restrictive applies (IPC §102.1).
• Existing installations (§102.2): Lawful existing systems may continue if maintained per original design and no new hazard is created.
• Additions/alterations (§102.4): Must conform to new system requirements but do not require the entire existing system to be brought up to current code. Must not make the system unsafe, unsanitary, or overloaded.
• Referenced standards (§102.8): Where the IPC conflicts with a referenced standard, the IPC governs.
• Code official authority (§102.9): Determines requirements not specifically covered by code.

Structural (IPC Chapter 3)

• Plumbing systems shall not impair the structural integrity of the building. Cutting, notching, and boring of structural members must comply with the International Building Code.
• Pipes must be protected from physical damage; sleeve pipes passing through concrete or masonry.

Key Concepts

Potable Water Protection & Cross-Connection Control - A cross-connection is any physical link between a potable water supply and a non-potable source. Prevention is the primary duty of the installer. - Air gaps and backflow preventers are the two fundamental protection methods. An air gap is always the most reliable protection.

Backflow Prevention Devices - Air Gap (AG): Physical separation; highest protection level. Required for high-hazard connections. - Reduced Pressure Zone (RPZ) Assembly: Used for high-hazard connections where an air gap is not feasible; contains two independently acting check valves and a relief valve. - Double Check Valve Assembly (DCVA): Used for low-hazard, non-health-risk cross-connections. - Pressure Vacuum Breaker (PVB): Used on irrigation systems; must be installed at least 12 inches above the highest downstream outlet. - Atmospheric Vacuum Breaker (AVB): Cannot be installed under continuous pressure.

IPC 2021 | 6 questions | 5% of exam

Key Concepts

Fixture Quality (Section 402) Plumbing fixtures must have smooth, impervious surfaces; porcelain enamel must be acid resistant. Specialty fixtures use stainless steel, soapstone, chemical stoneware, or plastic. Sheet copper ≥ 12 oz/sq ft (ASTM B152); sheet lead pans ≥ 4 lb/sq ft, coated with asphalt paint.

Minimum Fixtures by Occupancy (Section 403 / Table 403.1) Fixture counts are based on occupant load per IBC. Know these key thresholds: - Business: 1 WC per 25 (first 50), then 1 per 50; 1 lavatory per 40 (first 80), then 1 per 80; 1 drinking fountain per 100 - Educational: 1 WC per 50; 1 lavatory per 50; 1 drinking fountain per 100 - Assembly – Restaurants: 1 WC per 75 (M&F); 1 lavatory per 200 (M) - Assembly – Theaters: 1 WC per 125 (M), 1 per 65 (F) - Institutional – Hospitals: 1…

Key Concepts

Drainage Fixture Units (DFU) & Sizing DFUs are the load measurement basis for sizing all drainage piping. A standard lavatory = 1 DFU; water closet (private) = 3 DFU; water closet (public) = 4 DFU; bathtub/shower = 2 DFU; kitchen sink = 2 DFU. Pipe sizing is determined by cross-referencing total DFU load against IPC Table 710.1(1) for horizontal branches/building drain and Table 710.1(2) for stacks.

Horizontal Drain Slope Requirements (IPC Section 704) - Pipe sizes 2½" and smaller: minimum ¼" per foot (2.08% grade) - Pipe sizes 3" and larger: minimum ⅛" per foot (1.04% grade) - Maximum slope: ½" per foot (steeper = pipe considered vertical) - Horizontal drains must be installed without sags, humps, or offsets that could obstruct flow.

Key Concepts

Traps (IPC Chapter 10)

• Every fixture must have a trap; no fixture may be double-trapped
• Trap seal depth: Minimum 2 inches, maximum 4 inches of water seal (IPC §1002.2)
• Trap seal protection methods: venting (primary method), trap primers for floor drains, or air admittance valves where permitted
• Prohibited trap types (IPC §1003.1 / §1002.1): S-traps, bell traps, crown-vented traps, running traps (except where specifically permitted), and any trap that depends on moving parts to maintain the seal
• Trap-to-vent distance governs trap arm length; this distance is measured from the trap weir to the vent
• Each fixture trap must be accessible for maintenance

Key Concepts

Center-to-Center vs. End-to-End Pipe Length - Center-to-center (C-to-C): Distance between the centerlines of two connected fittings. - End-to-end (E-to-E): Actual cut length of pipe. Found by subtracting fitting allowances from C-to-C. - Formula: End-to-End = Center-to-Center − (Fitting Allowance A + Fitting Allowance B)

Fitting Allowances by Joint Type - Fitting allowances differ by material and joint type. Always look up values in the appendix data tables: - Threaded fittings: Use thread engagement depth (Data 1, Standard Weight Pipe table) - Copper fittings: Use socket depth (Data 4, Copper Tubes; Data 5, Elbows table) - PVC fittings: Use socket depth from fitting tables (Data 5–Data 8) - Welded fittings: Use center-to-face dimension minus weld gap allowance - The allowance is subtracted from each end of the run for each fitting connected.

(IFGC 2021 | 12 Questions, 11% of Exam)

Key Concepts

Scope (IFGC §101.2.2): The IFGC covers natural gas systems ≤125 psig and LP-gas systems ≤20 psig, from the point of delivery to the appliance shutoff valve outlet.

Gas Piping Materials (IFGC Chapter 4): - Metallic pipe: Black steel and wrought iron are standard; galvanized steel is acceptable. Threaded connections use approved pipe compounds (not Teflon tape on LP unless listed for that use). - Copper tubing: Only permitted for natural gas where not prohibited by the utility; not permitted for LP-gas with specific gravity >1.0 unless the tubing is internally tinned. - CSST (Corrugated Stainless Steel Tubing): Must be installed per the manufacturer's listing and bonded/grounded per IFGC §310.1 to protect against lightning-induced arc damage. - Polyethylene (PE) plastic: Underground use only; must be buried and cannot be used above grade. Requires a tracer wire and proper transition fittings at grade.

Key Concepts

Employer Responsibilities (29 CFR 1926 Subpart C)

Employers must initiate and maintain safety programs, including frequent and regular inspections of job sites, materials, and equipment. A competent person must conduct these inspections. Employers are responsible for instructing employees to recognize and avoid unsafe conditions.

Personal Protective Equipment (29 CFR 1926 Subpart E)

• Employers must provide and pay for all required PPE — employees cannot be charged for it.
• PPE selection must be based on hazard assessment of the specific task.
• Includes hard hats, eye/face protection, gloves, respirators, and fall protection harnesses.
• Respirators fall under 29 CFR 1926.103; a written respiratory protection program is required.