What is the name of a water supply pipe that extends vertically one full story or more to supply water to main branches or a group of fixtures?

• A. Main Line
• B. Riser
• C. Branch Line
• D. Drop Pipe

Answer: (B)

A riser is a vertical water supply pipe that runs through a building to deliver water to the main branches or groups of fixtures on successive floors. It acts as the building’s vertical backbone for distributing cold or hot water upward from the point where the service enters, and on each floor the branch lines tap off from the riser to feed fixtures such as sinks, toilets, and appliances. In multi-story buildings, there may be multiple risers to balance pressure and capacity, and they’re typically housed in a vertical chase or utility space with appropriate supports and insulation. By contrast, the main line brings water into the building from the street, branch lines extend from the risers to individual fixtures, and a drop pipe is a vertical segment that drops from a horizontal line to a fixture, not the continuous vertical distribution path through the building.