What does a horizontal branch drain do?

A horizontal branch drain is a critical component of a plumbing system that functions to receive wastewater from multiple fixture drains and convey it to larger soil or waste stacks. This aspect of the plumbing system allows for the efficient movement of sewage or greywater from various fixtures—such as sinks, showers, and toilets—ensuring that waste is directed towards the proper drainage or sewer system. The design and installation of horizontal branch drains follow specific plumbing codes to maintain system integrity and prevent issues such as blockages or backflow.

The other options do not accurately describe the role of a horizontal branch drain. For example, carrying water to ground levels does not encompass the primary function of collecting and transporting wastewater. Similarly, stating that it only connects to outdoor fixtures is misleading since horizontal branch drains are used throughout the entire plumbing system, both indoors and outdoors. Lastly, the treatment of wastewater is not a function of the horizontal branch drain itself; this process typically occurs at a sewage treatment facility or within a specific onsite treatment system, not within the drainage piping system.