Mississippi Plumbing

Key Concepts

Scope & Applicability (IPC 2021, Section 101–102) - The IPC applies to installation, alteration, repair, relocation, replacement, and maintenance of plumbing systems. Fuel gas systems fall under the International Fuel Gas Code, not the IPC. - Detached one- and two-family dwellings and townhouses ≤3 stories may comply with either the IPC or the IRC. - Where general and specific requirements conflict, the specific requirement governs. Where sections specify different materials or methods, the most restrictive governs (Section 102.1). - Existing systems may remain in use if maintained per original design and no hazard is created (Section 102.2).

(4 questions, ~6% of exam)

Key Concepts

Confined Space Identification & Classification (OSHA 29 CFR 1910.146)

A permit-required confined space (PRCS) has all three: (1) large enough for a worker to enter and perform work, (2) limited means of entry/exit, and (3) not designed for continuous occupancy — plus at least one serious hazard (hazardous atmosphere, engulfment risk, internal configuration that could trap a worker, or any other recognized serious safety/health hazard).

A non-permit confined space meets the first three criteria but contains no serious hazards.

Key Concepts

Placement Intervals (IPC Section 708) Cleanouts are required at specific maximum intervals along horizontal drain runs:

• Horizontal drains inside buildings: Cleanout required every 100 feet (30 480 mm)
• Building sewers and drains: Cleanout required every 100 feet
• Cleanouts must be installed at the junction of the building drain and building sewer
• Cleanouts are required at each change of direction greater than 45 degrees in horizontal drain piping

Cleanout Size Requirements - For pipes 4 inches and smaller: cleanout must be the same size as the pipe - For pipes larger than 4 inches: cleanout must be not less than 4 inches

Key Concepts

Minimum Fixtures by Occupancy (IPC Chapter 4, Table 403.1) Every building must have a minimum number of fixtures based on occupancy type and occupant load. Know that separate facilities are required for each sex when occupant load thresholds are met. Employee and public facilities have different minimums. Fixtures serving multiple purposes (employee/public) count toward both requirements.

Fixture Material Standards (IPC Section 402) - All fixtures must be smooth, impervious, and resistant to hot water, cleaning agents, and waste materials - Fixtures must be free from concealed fouling surfaces - Materials must conform to ASME, ANSI, or other referenced standards - Vitreous china, porcelain-enameled cast iron, porcelain-enameled steel, stainless steel, and plastic are acceptable materials when they meet…

Key Concepts

Temperature & Pressure Relief Valves (Section 504.4) - All storage water heaters operating above atmospheric pressure must have an approved, self-closing (levered) T&P relief valve conforming to ANSI Z21.22. - T&P valves must be installed in the shell of the tank, positioned to sense water in the top 6 inches (152 mm) of the tank. - Relief valves shall not be used to control thermal expansion — that's a separate function requiring a different device.

Relief Valve Discharge Piping (Section 504.5) - Discharge pipe must be the same size as the valve outlet — never reduced. - Must discharge full size to the floor, to an indirect waste receptor, or to the outdoors. - Pipe must terminate…

Key Concepts

Approved Materials & Standards

• All pipe, fittings, traps, and devices must bear manufacturer identification and markings per applicable standards (IPC §303.1).
• Plastic pipe, fittings, and components must be third-party certified to NSF 14 (IPC §303.3).
• Cast-iron soil pipe, fittings, and couplings must be third-party listed and labeled; certifiers must meet ASTM/CISPI Annex A or A1 inspection requirements (IPC §303.5).
• Materials must be installed per the standards under which they are approved. Where manufacturer instructions conflict with the code, the more restrictive provision applies (IPC §301.7, §303.2).

Water Service & Distribution Pipe — Approved materials include copper (Types K, L), CPVC, PEX, and ductile iron. Each must conform to its respective ASTM/AWWA standard.

(6 questions, 9% of exam | IPC 2021)

Key Concepts

Backflow Prevention Match the device to the hazard level. An air gap (double the pipe diameter, min. 1 inch) is the highest protection and is non-mechanical. A reduced pressure zone (RPZ) backflow preventer is required for high-hazard cross-connections. A double check valve assembly (DCVA) is used for low-hazard, non-health applications (e.g., irrigation without chemicals). Backflow preventers must be tested annually and installed accessible. IPC Section 608 governs cross-connection control.

Key Concepts

Pipe Support Intervals (IPC Table 308.5) Horizontal support spacing varies by material. Know these key values:

• Cast iron – 5 ft (at each joint and midspan, or every 10 ft with mid-span support)
• PVC/ABS/CPVC (≤1") – 3 ft horizontal; every other story vertical (max 10 ft)
• PVC/ABS (>1") – 4 ft horizontal
• Copper tube (≤1.25") – 6 ft horizontal; 10 ft vertical
• Copper tube (>1.25") – 10 ft horizontal
• Steel pipe (≤1") – 10 ft horizontal; 15 ft vertical
• Steel pipe (>1") – 12 ft horizontal
• CPVC – 3 ft horizontal; every floor vertical

Key Concepts

Drainage Fixture Units (DFU) DFU values quantify the load each fixture places on the drainage system. Key values from IPC Table 709.1: water closet = 4 DFU, bathtub/shower = 2 DFU, lavatory = 1 DFU, kitchen sink = 2 DFU, clothes washer = 2 DFU, floor drain = 2 DFU. A bathroom group (water closet + lavatory + tub/shower) = 6 DFU total.

Pipe Sizing — Horizontal Drains, Building Drains, and Sewers Size horizontal drainage piping using IPC Table 710.1(2). A 3-inch pipe at 1/4"/ft slope handles up to 20 DFU; a 4-inch pipe handles up to 160 DFU. Building sewers follow IPC Table 710.1(1). No horizontal drain pipe carrying water closet discharge may be less than…

Key Concepts

Core Definitions (IPC Chapter 2) - Backflow: Pressure in the water distribution system exceeding supply main pressure, causing reverse flow into the potable supply. - Backsiphonage: Backflow caused by negative pressure (below atmospheric) in the potable system — a siphoning effect pulling contaminated water back in. - Backpressure: Downstream pressure exceeding supply pressure, forcing flow backward. Low head backpressure = ≤4.33 psi (≤29.88 kPa), equivalent to a 10-foot column of water. - Cross connection: Any arrangement (backflow connection) whereby backflow into the potable supply is possible.

Key Concepts

Trap Seal Depth Requirements

• Trap seals must be a minimum of 2 inches and a maximum of 4 inches deep (IPC Section 1002.2)
• Prohibited trap types include: bell traps, crown-vented traps, "S" traps, drum traps (except for special applications), and any trap with interior partitions — these are expressly forbidden
• Each fixture must have an individual trap — double trapping (one trap serving a fixture already trapped) is prohibited

Fixture Trap Installation — Distance Limitations

• The trap must be located as close to the fixture as possible
• Maximum distance from trap weir to vent fitting: 6 feet for a 1.25" pipe, 8 feet for 1.5" pipe, 10 feet for 2"…

Key Concepts

Developed length is the total length of pipe measured along the centerline of the pipe and fittings, including all bends, offsets, and changes in direction — not a straight-line (end-to-end) distance.

• Center-to-center measurement: Distance from the center of one fitting to the center of another. This is the field measurement you start with.
• End-to-end (face-to-face) measurement: The actual pipe cut length, calculated by subtracting the fitting allowances (makeup distances) from the center-to-center measurement.
• Fitting allowance (also called "fitting makeup" or "thread engagement"): The amount of pipe that enters into a fitting. This varies by fitting type and pipe size.

Key Concepts

Isometric drawings represent 3D piping systems on a 2D plane using 30° angles for horizontal runs and true vertical lines. Every measurement you calculate comes from one of three relationships: center-to-center (c-c), end-to-end (e-e), or diagonal/offset.

Center-to-Center (C-C): The distance measured from the centerline of one fitting to the centerline of the next. This is read directly from the isometric drawing and is your starting point for all pipe cut calculations.

End-to-End (E-E) / Cut Length: The actual length of pipe you cut. You subtract fitting allowances (also called "makeup" or "thread engagement") from both ends of the c-c measurement.

E-E = C-C − (Fitting Allowance × 2) For threaded fittings, each fitting allowance is…

Key Concepts

PVC Plastic Pipe (IPC Section 705)

• Solvent cement is the standard joining method; requires primer and cement compatible with the pipe material
• Mechanical, threaded, and push-fit joints are also permitted
• Solvent-cemented joints require the surfaces to be clean and dry; cement must be applied to both pipe and fitting socket

Copper and Copper-Alloy Pipe/Tubing

• Solder joints: Use lead-free solder (≤0.2% lead) for potable water systems — this is a hard rule
• Brazed joints: Higher-strength alternative using filler metal with melting point above 1000°F (538°C)
• Press-connect joints: Factory-engineered fittings requiring approved press tools
• Push-fit joints: No tools or adhesive required; used for repairs and accessible locations
• Mechanical joints:…