Roof Drains Josam's roof drains include Large Sump, Medium Sump, Small Sump, Sill Type, Promenade Top, Parapet Type, Flow Control Type, Overflow Type, and Green Roof Drains. They feature the WEJLOC® clamping system. The design includes a gravel stop that prevents roof debris from entering the drain, ensuring complete drainage through "V" notch weirs while offering secure flashing with a positive non-puncturing bond to mating flange of collar. Filter by Large Sump Medium Sump Small Sump Sill Type Promenade Top Parapet Type Flow Control Type Overflow Type Green Roof Drain Miscellaneous Roof Drains & Accessories PVC Roof Drain Body RD-300 – Lite Line: PVC Roof Drain Body w/ CI Clamp Ring & Dome.