Sedimentation Drain Design

Drain Sizing

The time it takes to drain the sed tank can be approximated by:

where W_SedBay is the width of a single sedimentation bay, AN_SedPlate is the angle of the bottom slopes from the horizontal, L_Sed is the length of the sedimentation tank, D_Valve is the diameter of the drain valve, HW_Sed is the water height in the sedimentation tank, and K_GateValve + K_Exp is the total head loss through the valve.

For any given time, the idealized valve diameter may be calculated using the above equation. This idealized diameter is rounded up to the next possible nominal diameter.

Couplings

The calculated nominal diameter is that of the slip side of the adapter and is used to calculate its corresponding inner and outer diameters. The outer diameter of the slip side is also the inner diameter of the threaded side. The outer diameter of the threaded side is used as the inner diameter of the valve which fits it.

Drain Slopes

Since the center of the valve is aligned with the floor of the sedimentation tank, slopes are required in the floor of the tank. The slopes have a width equal to the diameter of the valve and a depth equal to half the diameter (placing the center of the valve at-grade) with a slope of 30 degrees.

Gate Valves

Gate valves are placed in every bay of every sedimentation tank at-grade to allow for draining.