Written by IAPMO 1:56 pm Uniform Codes Spotlight


August 31

From the 2021 UPC Illustrated Training Manual, Chapter 9, VENTS

911.3 Relief Vent. A 2 inch (50 mm) relief vent shall be provided for circuit-vented horizontal branches receiving the discharge of four or more water closets when connecting to a drainage stack that receives the discharge of soil or waste from upper horizontal branches.

There are two conditions that mandate the installation of a relief vent for a circuit-vented horizontal branch:

1) when the circuit-vented horizontal branch receives the discharge of four or more water closets, and

2) when the circuit-vented horizontal branch connects to a stack that receives discharges from upper floor fixtures.

See Figure 911.3.

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.)


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Last modified: August 31, 2023