What type of vent connects to a horizontal branch and can vent multiple traps?

A circuit vent is specifically designed to connect to a horizontal branch of plumbing and provides ventilation to multiple traps. It allows for the equalization of pressure in a drainage system, which is crucial for proper drainage and preventing trap siphonage. The circuit vent provides a pathway for air to enter the drainage system, thereby ensuring that wastewater flows smoothly and the traps retain their water seal, which blocks sewer gases from entering the living space.

This type of vent is commonly used in configurations where multiple fixtures are close together, allowing one vent pipe to serve several downstream traps efficiently. The design promotes better airflow and reduces the amount of vent piping needed, ultimately simplifying the plumbing layout.

In contrast, a waste vent generally serves to ventilate a single fixture or trap and does not connect to multiple traps simultaneously. A stack vent extends vertically above the highest fixture and is also not limited to connecting to horizontal branches. A relief vent is used in systems to relieve pressure but does not specifically connect to multiple traps in the same way that a circuit vent does. Therefore, the circuit vent stands out as the best choice for this particular scenario.