In the isometric below, why is the cleanout (CO) installed at the base of the stack, ahead of the bend into the building drain?
[3" WASTE STACK]
|
|
CO ----> +---+---+ ----> 4" BUILDING DRAIN --->
(1/4 bend)
Base-of-stack cleanout
Not quite. The answer is C: Because each horizontal drainage pipe needs a cleanout at its upper terminal, and the building drain begins at the base of the stack
The 4-inch building drain is a horizontal drainage pipe, and the code requires a cleanout at the upper terminal of each horizontal drain. Placing it right where the stack turns into the building drain gives one accessible point from which the horizontal run can be rodded, in the direction of flow, and it is where debris from the stack tends to collect.
Reference: WAC 2021 51-56-0700, §707.4 (Cleanout at upper terminal of each horizontal drain)
Checked against the official text
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