How far downstream of the base of a drain stack must horizontal branches connect?

The correct answer indicates that horizontal branches must connect at least 10 pipe diameters downstream of the base of a drain stack. This requirement is an important plumbing code stipulation designed to ensure proper drainage and venting in a plumbing system.

The rationale behind this regulation is primarily related to the flow dynamics within the drain system. Connecting a horizontal branch too close to the drain stack can lead to issues with siphoning or turbulence, which could impede the flow of wastewater. By maintaining a distance of 10 pipe diameters, the design helps establish a more stable flow pattern, reducing the risk of trapped air or backflow that could result from an improperly placed horizontal connection.

The specified distance ensures that the wastewater has sufficient space to achieve a smooth, uninterrupted flow into the main drain system. Proper adherence to this guideline helps maintain the efficiency of the plumbing system while minimizing potential for clogs or other drainage problems that could arise from poorly positioned branches.