|1. A vertical, or 45°, relief vent of the continuous waste-and- vent type formed by the extension of an upright wye-branch inlet of the horizontal branch to the stack. It becomes a dual yoke vent when two horizontal branches are vented by the same relief vent. Its purpose is to prevent pressure changes in the stacks.
2. A pipe connecting upward from a soil, or waste stack, to a vent stack for the purpose of preventing pressure changes in the stack.