When connecting horizontal branches downstream of a drainage stack, how many pipe diameters downstream should they connect?

The requirement for connecting horizontal branches downstream of a drainage stack is based on ensuring smooth flow and minimizing turbulence within the drainage system. Connecting the horizontal branches at a distance of 10 pipe diameters downstream from the stack allows for the proper distribution of flow, reducing the potential for backpressure and facilitating a more effective drainage operation.

This distance helps to ensure that the flow from the stack has stabilized and is not disrupted by incoming flows from the connected horizontal branches. Additionally, it allows for the equalization of pressures and velocities in the piping system as it transitions from the vertical to the horizontal plane. This practice is crucial in maintaining the integrity and efficiency of the plumbing system, preventing blockages and ensuring compliance with plumbing codes.

Understanding these principles is essential for effective plumbing design and operation, ensuring that installations function properly and adhere to safety and performance standards.