A 6" branch lateral requires what size main?

When determining the appropriate size of the main for a 6" branch lateral, it's essential to consider the flow requirements and pressure drop that would occur within the piping system. A branch lateral is designed to connect to a main and extend to where fluid is needed, so it must be adequately supported by the main to ensure efficient and effective flow.

In this case, an 8" main is typically the minimum size required to effectively support a 6" branch lateral. However, for optimal performance and to accommodate potential increases in flow or changes in pressure, a 10" main is recommended. This larger size allows for a smoother flow transition and reduces the risk of experiencing high velocities or turbulent flow, which can lead to wear, pressure loss, or noise issues in the piping system.

Selecting a main that is larger than the branch lateral provides a better system design by ensuring that the main can handle the cumulative flow from the branch without restrictions or bottlenecks. Therefore, the correct answer is 10", as it balances efficient flow with safety and performance considerations within high-pressure piping systems.