Choosing Between Sock-Wrapped and Sand-Slot Pipes
If fine sand or silt gets into subsurface (tile) drain pipes, it can remain near the entry point, build up over time, and cause drain clogging. If drain sedimentation is a problem, use either sock- wrapped or sand-slot pipe (Figure 1). A sand- slot pipe is also known as narrow-slot, knife-cut, or fine-slot. A sand-slot pipe has a narrow slot width of about 0.015 inches to keep sediment out of the drain pipe. Typically, a regular-perforated rectangular-slotted pipe is wrapped with a knitted- sock envelope. Other pipes can also be wrapped with a knitted sock to give the same drainage performance. For more information about regular-perforated pipes, see Ghane (2022b).
This bulletin describes the condition where sock- wrapped and sand-slot pipes are needed. The bulletin also compares the properties of three 4-inch diameter pipes: sock-wrapped, 8-row sand- slot, and 4-row sand-slot pipes. The evaluated properties include water entry into the pipe, water-table drawdown, drain spacing, and cost effectiveness. This bulletin is based on scientific research conducted on CARRIFF Type A circular-knitted-sock geotextile envelope and commonly manufactured sand-slot pipes in the Midwest USA (Ghane, 2022a; Ghane et al., 2022).