1. A vent arrangement for a group of plumbing fixtures; consists of a vent pipe which is connected to the waste or soil branch immediately before the first fixture of the group and immediately before the last fixture of the group; the two connections are then “looped” together and connected to the vent stack.
2. The same as a circuit vent except that it loops back and connects with a stack vent extension of the soil stack instead of a separate vent stack.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.