1.3 General Regulations: Prohibited Fittings, Pipe Protection, Nail Plates, Sleeves, & Trenching (UPC Chapter 3)

Why Chapter 3 Shows Up Everywhere

Chapter 3 of the UPC holds the "general regulations." These rules apply in every other chapter: approved materials and markings, prohibited fittings, pipe protection, hangers, trenching, and test gauges. Part 1 of the Washington exam draws on UPC Chapters 1 through 10, so expect short, direct questions here. Typical examples ask which fitting is prohibited, what gauge a nail plate must be, or how deep backfill must go.

Materials, Marking, and Workmanship

• 301.2 Minimum standards: Pipe, fittings, traps, fixtures, and devices must be listed or labeled by a listing agency and meet the referenced standards. Plastic pipe and fittings other than gas components must comply with NSF 14.
• 301.2.1 Marking: Each length of pipe and each fitting must carry the manufacturer's mark, plus the weight and quality where the standard requires it.
• 301.3 Alternates: Equivalent systems, methods, or devices may be approved by the AHJ with technical documentation. Washington's amendment adds that a disapproval must be explained in writing.
• 309 Workmanship: It is unlawful to hide cracks or holes with welding, solder, paint, wax, tar, or sealants (309.2). Burred ends must be reamed to full bore (309.3).

Prohibited Fittings and Practices (UPC 310)

Section 316.1 requires proper increasers or reducers between pipe sizes. A copper alloy or cast-iron cleanout body may not be used as a reducer or adapter from cast-iron drainage pipe to IPS pipe.

Independent Systems (UPC 311)

Each new building must have a drainage system separate and independent from any other building, with its own sewer connection where available. The exception: when one building stands behind another on an interior lot and no private sewer can reach the rear building, the front building's drain may be extended to it.

Protection of Piping (UPC 312)

• 312.2: Plumbing piping may not be directly embedded in concrete or masonry. Provide for expansion, contraction, and settlement.
• 312.3: Drainage piping made of materials not approved for use in a building may not be installed within 2 feet of the building or less than 1 foot below the ground surface.
• 312.6 Freezing (Washington amendment): Water, soil, or waste pipe outside a building, in attics or crawl spaces, or in exterior walls must be protected from freezing where necessary. Washington adds that all hot and cold water pipes outside the conditioned space must be insulated. The 2015-edition amendment set a minimum of R-3.
• 312.7 (Washington amendment): Penetrations of fire-resistance-rated assemblies are protected as the building code requires. Washington does not adopt UPC Chapter 14, Firestop Protection.
• 312.9 Steel nail plates: Plastic, copper, or copper-alloy piping that passes through framing within 1 inch of the exposed framing face needs a steel nail plate at least No. 18 gauge (0.0478 inch). The plate must extend at least 1-1/2 inches beyond the outside diameter of the pipe.
• 312.10 Sleeves: Piping through concrete or masonry walls and concrete floors needs sleeves, except where the opening is drilled or bored. The pipe may not carry building loads. The annular space in exterior walls must be sealed watertight.
• 312.11 Structural members: A member weakened by cutting or notching must be reinforced, repaired, or replaced as the building code requires. Boring and notching limits come from the building code, not the UPC.
• 312.12 Rodentproofing: Strainer openings on drain inlets may not exceed 1/2 inch. Pipe openings through walls and floors get metal collars. Tub waste openings into crawl spaces at or below the first floor get metal collars or screen with no opening over 1/2 inch.
• 312.13 and 312.14 Sunlight: ABS and PVC may not be exposed to direct sunlight unless protected with water-based synthetic latex paint. PVC may also be wrapped with tape at least 0.04 inch thick.

Trenching, Excavation, and Backfill (UPC 314)

1. 314.1: A trench deeper than a footing and parallel to it must stay outside a 45-degree line from the bottom exterior edge of the footing.
2. 314.2: Tunnels need 2 feet of clear height above the pipe and are limited to half the trench depth, with a maximum length of 8 feet. A drive pipe must be at least one size larger than the pipe being laid.
3. 314.3: Excavations for building drainage inside the walls must be open trench and stay open until the piping is inspected, tested, and accepted.
4. 314.4: Backfill in thin layers to 12 inches above the top of the pipe with clean earth free of stones, boulders, cinders, frozen earth, or debris. After that, machines may finish the backfill.
5. 314.4.1 Thermoplastic sewer pipe: Make the trench 1.25 × OD + 12 inches or OD + 16 inches wide. Bed the pipe in at least 4 inches of granular fill. Compact the sides in 6-inch layers to at least 12 inches above the pipe, at 85% standard proctor density or better.

Section 313.5 also requires underground piping to be laid on a firm bed for its entire length.

Test Gauges (UPC 318)

The gauge's range may not exceed twice the test pressure (318.5).