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IAPMO Uniform Codes Spotlight

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From the 2015 UPC Illustrated Training Manual

711.0 Suds Relief.
711.1 General. Drainage connections shall not be made into a drainage piping system within 8 feet (2438 mm) of a vertical to horizontal change of direction of a stack containing suds-producing fixtures. Bathtubs, laundries, washing machine standpipes, kitchen sinks, and dishwashers shall be considered suds-producing fixtures. Where parallel vent stacks are required, they shall connect to the drainage stack at a point 8 feet (2438 mm) above the lowest point of the drainage stack.
(1) Single-family residences
(2) Stacks receiving the discharge from less than three stories of plumbing fixtures

The above-named suds producing fixtures discharge high-sudsing detergents that, when mixed with other liquid wastes (in addition to air in a stack), create areas of increased turbulence in lower portions of soil stacks. The liquid wastes, being heavier than suds, will flow through the suds-loaded piping without carrying the suds discharge along with the flow (see Figure 711.1a). However, the suds become compressed, forcing them to move through any available path of relief. The relief path may be any of the branches connected to the building drain or a vent stack or branch vents. High suds pressure will blow trap seals, leaving residue in the fixtures and allowing sewer gas to enter the building (see Figure 711.1b). Any vertical-to-horizontal change of direction of a stack receiving the discharge of suds-producing fixtures has the potential to create a sudsing problem.

The 2015 Uniform Plumbing Code Illustrated Training Manual eBook is available for purchase here.

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