What is the minimum design velocity for a sewer system?

The minimum design velocity for a sewer system is established to ensure effective self-cleansing of the pipes and to prevent clogging. A velocity of two feet per second is recognized as the threshold for preventing sedimentation in sewage systems. This velocity helps in maintaining a flow that is sufficient to keep solids suspended and moving through the system, thereby reducing the risk of blockages and associated problems.

This specific velocity is supported by design guidelines and empirical observations, which indicate that flows below this threshold can lead to the deposition of solids within the sewer system. The objective is to achieve a balance where the flow is high enough to carry materials effectively without incurring excessive turbulence or energy costs. Thus, two feet per second stands as the minimum recommended velocity for gravity sewers in standard practice.