From the 2021 UPC Illustrated Training Manual, Chapter 6, WATER SUPPLY AND DISTRIBUTION
603.4.4 Connections. Direct connections between potable water piping and sewer-connected wastes shall not be permitted to exist under any condition with or without backflow protection. Where potable water is discharged to the drainage system, it shall be by means of an approved air gap of two pipe diameters of the supply inlet, but in no case shall the gap be less than 1 inch (25.4 mm). Connection shall be permitted to be made to the inlet side of a trap provided that an approved vacuum breaker is installed not less than 6 inches (152 mm), or the distance according to the device’s listing, above the flood-level rim of such trapped fixture, so that at no time will such device be subjected to backpressure.
Under no circumstance should there be a direct connection of the potable water supply to the drainage system. Normally this is not an issue. A plumber should understand the reasons for this and never intentionally tie the two systems together. But sometimes it is forgotten that a relief line from a pressure relief valve or temperature pressure relief valve or the discharge from a water treatment system is a direct connection to the potable system. Lines such as this shall discharge to the drainage system through an airgap two times the diameter of the pipe or a minimum of one inch (see Figure 603.4.4).
The discharge line of the AVB can connect to the inlet side of a trap, which is the tailpiece of a fixture above the trap seal. The AVB is required to be installed a minimum of six inches above the flood rim of the fixture. The measurement is from the critical level of the device to the flood rim.
The 2021 Uniform Plumbing Code Illustrated Training Manual is available for purchase here.
(This is not to be considered the official position of IAPMO, nor is it an official interpretation of the Codes.)
IAPMO develops and publishes the Uniform Plumbing Code®, the most widely recognized code of practice used by the plumbing industry worldwide; Uniform Mechanical Code®; Uniform Swimming Pool, Spa and Hot Tub Code®; and Uniform Solar Energy, Hydronics and Geothermal Code™ — the only plumbing, mechanical, solar energy and swimming pool codes designated by ANSI as American National Standards — and the Water Efficiency Standard (WE-Stand)™. IAPMO works with government, contractors, labor force, and manufacturers to produce product standards, technical manuals, personnel certification/educational programs and additional resources in order to meet the ever-evolving demands of the industry in protecting public health and safety.
Last modified: June 22, 2023