What Are Branch Drain Lines?
Branch drain lines are plumbing drain lines that carry the waste of two or more plumbing fixtures to a branch drain line. A branch drain line is typically connected to the main stack, which is located in the basement or interior of a building. The branch drain carries wastewater away from plumbing fixtures, such as sinks and toilets, to the main plumbing stack for dispersal into the municipal sewer system. The end of each branch drain must be connected to the main plumbing stack through an air gap an unobstructed vertical space that allows wastewater to flow into it but not back out again.
Each plumbing fixture has its own drain trap (P-trap), which traps wastewater flowing out of it before sending its contents down the pipe and into the drain line. The branch drains extend from each plumbing fixture’s trap to the air gap opening in the plumbing stack, and they must be connected by a vent.
Branch drain lines are common for plumbing systems that include sinks, showers, bathtubs, and washing machines. They collect wastewater from all plumbing fixtures on one floor of a building or home, which helps simplify plumbing problems if only one fixture is experiencing drainage problems.
What Is a Branch Sewer Line?
A branch sewer is part of an underground network of pipes that moves sewage to treatment plants or outfall points where it can be safely dispersed. Much like branch drain lines carry waste to other plumbing fixtures, branch sewers disperse wastewater to larger sewers that lead to collection mains. Each branch sewer pipe is connected to one or more plumbing stacks that disperse wastewater into the main sewer line for dispersal into a sewage treatment plant.
The branch drain lines are usually thinner pipes than the branch sewers, but both systems distribute wastewater from plumbing fixtures to larger sewers throughout a municipal district. The branch drain lines are typically located in buildings’ basements, while the branch sewers are located underneath streets or sidewalks. Branch sewers can be large enough to accommodate emergency vehicles and handle traffic flow, while some also use grates on top of them to allow rainwater to enter them when it rains in order to prevent floods during storms.
