- Zurn Z886 6 in [152 mm] wide pre-sloped trench drainage system. High density polyethylene structural composite drain channel with .75 percent bottom slope. All sections are 80-inch modular lengths with integral top frame, inter-locking ends and radiused bottom. Combination tie-down/leveling devices at 20-inch intervals. Furnished with heavy-duty Dura-coated cast iron grate unless otherwise specified. USA configurable.