6.1 DWV Materials, Joints, & Changes in Direction (UPC 701, 704–706; WA 701.2)

Why Fittings and Materials Matter on Part 2

The Part 2 drawing shows DWV piping, fittings, and cleanouts. Knowing which fitting belongs at each change of direction, and which material may go underground, helps you spot the violations questions ask about (Section 11.4). Part 1 questions test the same rules directly.

Drainage Materials (Table 701.2 and Washington 701.2)

UPC Table 701.2 lists the approved materials and whether each may be used underground, aboveground, or for building sewers. Common entries include ABS and PVC Schedule 40 (solid and cellular core), co-extruded ABS and PVC, cast iron (ASTM A74, ASTM A888, CISPI 301), copper and copper-alloy Type DWV, galvanized steel and malleable iron, stainless steel 304 and 316L, polyethylene (building sewer), and vitrified clay (extra strength). Washington's amendment to 701.2 adds limits:

Other material rules:

• 701.4 Continuous wastes and tailpieces: Use drainage materials, but where exposed or accessible they may be seamless drawn brass at least No. 20 B&S gauge.
• 701.5 Sheet lead: at least 4 lb per sq ft for safe pans and 3 lb per sq ft for flashings. Lead bends and traps must be at least 1/8 inch thick.
• 701.3 Fittings: Drainage-type fittings, the same diameter as the pipe, with a smooth waterway, made to allow 1/4 inch per foot grade. Threaded pipe uses recessed drainage fittings, and burred ends are reamed.

Fixture Connections (UPC 704)

• 704.1: Drainage piping must have approved inlet fittings, located for the size and type of fixture to be connected.
• 704.2: Two fixtures set back-to-back or side-by-side, within the allowed trap-to-vent distance, may share a single vertical drain. Each must waste separately into an approved double fixture fitting with inlets at the same level.
• 704.3 (Washington amendment): Unless a fixture is specifically required to be indirect, or the AHJ approves otherwise, all fixtures, drains, appurtenances, and appliances must be directly connected to the drainage system.

Joints (UPC 705)

Changes in Direction (UPC 706)

Section 706.1 requires changes in direction to use approved fittings with the angle of a 1/16 bend, 1/8 bend, or 1/6 bend, or fittings of equivalent sweep.

Multiple inlets at one level (706.2): No fitting with more than one inlet at the same level may be used unless it is built so discharge from one inlet cannot readily enter another. A double sanitary tee is permitted only when the barrel is at least two pipe sizes larger than the largest inlet. The recognized pipe sizes for this count are 2, 2-1/2, 3, 3-1/2, 4, 4-1/2, 5, 6 inches, and so on. For example, 2-inch inlets need at least a 3-inch barrel (2 to 2-1/2 is one size, and 3 is the second).

Why a sanitary tee is prohibited for horizontal-to-horizontal flow: its short-radius turn shoots water across the fitting and slows it, so solids settle and the line stops up. A wye with a 1/8 bend keeps the flow sweeping in the direction of travel.

Related Rules

• 310.1: No double hub, single or double tee branch, side inlet quarter bend, running thread, band, or saddle as a drainage fitting (Section 1.3).
• 310.3: No waste connection to a closet bend or water closet stub.
• 316.1: Use proper increasers and reducers between sizes.
• 711.1 Suds relief: Do not connect any drain within 8 feet of the base of a stack, at its vertical-to-horizontal change, if the stack carries suds-producing fixtures. Those fixtures are bathtubs, laundries, washer standpipes, kitchen sinks, and dishwashers. The rule does not apply to single-family residences or to stacks receiving discharge from fewer than three stories of fixtures.