2.2 Fixture Materials, Prohibited Fixtures, Overflows, Waste Outlets & Fixture Setting

Why this section matters

Questions in the Fixtures and Fittings area often ask what a fixture must be made of, which fixtures are banned, and how fixtures connect to the drainage system. The 2021 IPC arranges most fixture sections alphabetically: 407 Bathtubs, 419 Lavatories, 421 Showers, 422 Sinks, 424 Urinals, 425 Water closets. Tab them that way.

Fixture quality and materials (401–402)

• 402.1: Fixtures must be made of approved materials with smooth, impervious surfaces, free of defects and concealed fouling surfaces. Porcelain enamel must be acid resistant.
• Fixtures must meet their standards:
  • vitreous china, ASME A112.19.2/CSA B45.1;
  • enameled cast iron and steel, ASME A112.19.1/CSA B45.2;
  • stainless steel, ASME A112.19.3/CSA B45.4;
  • plastic fixtures, CSA B45.5/IAPMO Z124.
• 402.2: Specialty fixtures not covered elsewhere are stainless steel, soapstone, chemical stoneware or plastic. They may instead be lined with lead, copper-base alloy, nickel-copper alloy or corrosion-resistant steel.
• 402.3: Sheet copper for general use weighs at least 12 oz per square foot.
• 402.4: Sheet lead for pans weighs at least 4 lb per square foot and is coated with asphalt paint.

Prohibited fixtures (401.2)

The 2021 IPC names three prohibited items:

1. Water closets with a concealed trap seal or an unventilated space, or with walls not fully washed at each discharge.
2. Water closets that let the contents of the bowl siphon back into the tank.
3. Trough urinals.

Other bans live in the trap and drainage chapters. Section 1002.3 bans S-traps, bell traps, drum traps and traps with moving parts. Section 1002.6 bans building traps. Section 707.1 bans saddle fittings and concrete joints. Be ready to say which section a ban comes from.

Overflows (405.8)

• An overflow must be designed so standing water does not rise in it when the stopper is closed, and no water remains in it when the fixture is empty.
• 405.8.1: The overflow must discharge into the drainage system on the inlet or fixture side of the trap. If it connected downstream of the trap, sewer gas would bypass the seal.
• Exception: a flush tank's overflow discharges into the water closet or urinal it serves. Section 415.3.2 adds that the overflow must be sized for the tank's maximum fill rate, with its opening above the bowl's flood level rim.

Waste outlets and strainers

The minimum trap size comes from Table 709.1. A shower with a total flow of 5.7 gpm or less uses a 1-1/2-inch trap, and higher-flow showers need larger traps (section 5.1).

Slip joints (405.9)

• Slip joints need an approved elastomeric gasket and may be installed only on the trap outlet, the trap inlet and within the trap seal. Section 1002.2 repeats this.
• Fixtures with concealed slip joints need an access panel or utility space at least 12 inches in its smallest dimension, or another approved arrangement, so the joints can be inspected and repaired.
• A bathtub's waste and overflow behind a finished wall is the usual case where an access panel is needed.

Setting fixtures (405.4–405.6)

• Floor-outlet fixtures connect through a floor flange, or a waste connector and gasket tested to ASME A112.4.3. The flange must be attached to the drain and anchored to the structure.
• Floor flange minimums (405.4.1):
  • copper alloy, 0.125 inch thick;
  • plastic, 0.25 inch thick;
  • cast iron or galvanized malleable iron, 0.25 inch thick with a 2-inch caulking depth;
  • hard lead, 1 lb 9 oz.
  • Closet bolts and screws must be copper alloy, and the flange is fastened with corrosion-resistant screws or bolts.
• Wall-hung water closets hang on a concealed metal carrier (ASME A112.6.1M or A112.6.2) attached to the structure, so no strain reaches the connector (405.4.3).
• Joints where fixtures meet walls and floors must be sealed (405.6).
• Water closet connections (425.4): a 4 × 3-inch closet bend is acceptable. Where a 3-inch bend is used, install a 4 × 3-inch flange to receive the horn. Section 704.2 says a 4 × 3 flange or bend is not an illegal reduction in the direction of flow.

Water closets and urinals (424–425)

• 425.2: Water closets in public or employee toilet facilities must have elongated bowls.
• 425.3: Seats must be smooth and nonabsorbent. Public and employee seats must be the hinged open-front type.
• 425.1.3: Dual-flush water closets must comply with ASME A112.19.14.
• 424.1: Urinals must meet ASME A112.19.2/CSA B45.1, ASME A112.19.19 for nonwater (waterless) urinals, or CSA B45.5/IAPMO Z124, plus the water limits in 604.4.

Showers (421)

Sheet lead and sheet copper liners must be insulated from other metals by 15-pound asphalt felt or an equivalent.

Exam traps

• Overflow connects on the inlet side of the trap, never to a vent or downstream of the trap.
• Shower strainer openings must be at least 1/4 inch. That is a minimum, not a maximum.
• Trough urinals are banned by 401.2.
• Public water closets need elongated bowls and open-front seats.