The minimum scouring velocity normally used for sanitary collection lines is

The minimum scouring velocity normally used for sanitary collection lines is

• A. 1.0 ft/sec
• B. 2.0 ft/sec
• C. 5.0 ft/sec
• D. 10.0 ft/sec

Answer: (B)

Scouring velocity is the minimum flow speed needed to keep the solids in wastewater moving and prevent them from settling to the bottom of the pipe. For sanitary collection lines, keeping the flow at about two feet per second is a common design target because this speed is typically enough to suspend domestic solids under normal conditions, reducing the risk of sediment buildup that can cause blockages and odors. If the flow is slower than this, sediments settle and accumulate, leading to deposits that narrow the sewer and complicate maintenance. Velocities much higher than this, while better at keeping everything suspended, waste energy by increasing head loss and can cause unnecessary wear on pipes. So, two feet per second strikes a practical balance between keeping solids in suspension and avoiding excessive energy use, which is why it’s the standard answer.

Scouring velocity is the minimum flow speed needed to keep the solids in wastewater moving and prevent them from settling to the bottom of the pipe. For sanitary collection lines, keeping the flow at about two feet per second is a common design target because this speed is typically enough to suspend domestic solids under normal conditions, reducing the risk of sediment buildup that can cause blockages and odors. If the flow is slower than this, sediments settle and accumulate, leading to deposits that narrow the sewer and complicate maintenance. Velocities much higher than this, while better at keeping everything suspended, waste energy by increasing head loss and can cause unnecessary wear on pipes. So, two feet per second strikes a practical balance between keeping solids in suspension and avoiding excessive energy use, which is why it’s the standard answer.