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Where sinks, laundry trays, laundry washing machines, bathtubs, and similar fixtures in which detergents producing suds are normally used and discharged at an upper floor level into a soil or waste stack that also serves fixtures in other occupancy units at a lower floor level, the drainage and vent piping for such lower fixtures shall be arranged so as to avoid connection to suds pressure zones in the sanitary drainage and vent systems. If connected to the sanitary system, a suds relief vent relieving to a nonpressure zone shall be provided at each suds pressure zone where such connections are installed. The diameter of such relief vent shall be at least three-quarters the diameter of the piping in which the pressure zone occurs, but not less than 2 inches (51 mm). Suds pressure zones shall be considered to exist at the following locations in sanitary drainage and vent systems when the piping serves fixtures on two or more floors that receive wastes that contain detergents producing suds:
  1. In a soil or waste stack a zone shall be considered to exist in the vertical portion within 40 stack diameters of the base fitting.
  2. In the horizontal drain at the base of a soil or waste stack a zone shall be considered to exist in the horizontal portion within 10 stack diameters of the base fitting. Where a 60-degree (1.05 rad) or 90-degree (1.57 rad) fitting is installed in the horizontal drain, a zone shall be considered to exist in the horizontal portion within 40 drain diameters upstream of and 10 drain diameters downstream of the fitting in accordance with Figure 704.6.
  3. In a soil or waste stack offset of 60 degrees (1.05 rad) or 90 degrees (1.57 rad), a zone shall be considered to exist in the vertical portion of the stack within 40 stack diameters of the base fitting for the upper section of the stack. The zone shall be considered to exist in the horizontal offset within 10 stack diameters of such base fitting and within 40 stack diameters of the top fitting for the lower section of the stack.
  4. In a vent stack that has its base connected to a suds pressure zone in the sanitary drainage system, a zone shall be considered to exist in the portion of the vent stack extending from its base connection up to the lowest branch vent fitting located above the level of the suds pressure zone in the sanitary drainage system.
FIGURE 704.6
SUDS PRESSURE ZONES

Related Code Sections

704.6 Sanitary Drainage, Suds Pressure Zones Vents
and vent piping for such lower fixtures shall be arranged so as to avoid connection to suds pressure zones in the sanitary drainage and vent systems. If ...
704.6 Sanitary Drainage, Suds Pressure Zones Vents
and vent piping for such lower fixtures shall be arranged so as to avoid connection to suds pressure zones in the sanitary drainage and vent systems. If ...
704.6 Sanitary Drainage, Suds Pressure Zones Vents
, the drainage and vent piping for such lower fixtures shall be arranged so as to avoid connection to suds pressure zones in the sanitary drainage ...
Reference Standard 16 Plumbing and Gas Piping [PDF] (page 45)
at least 3 ft. above the floor level. See Figure RS 167 for typical installation. P109.10 Suds Pressure Zones Vents.(a) Where sinks, laundry trays ...
Reference Standard 16 Plumbing and Gas Piping [PDF] (page 5)
Stack Venting P109.7 Common Vents P109.8 Fixture Vents P109.9 Relief Vents P109.10 Suds Pressure Zones Vents P109.11 Permitted Combination Waste and Vent ...