Jabsco 1/2" Vented Loop 1. Vented Loop Vented loops are anti-siphon safety devices for use with both manual and electric marine toilets installed below the waterline (static or heeled) Specifications for Jabsco 1 1/2" Vented Loop: Manufacturer: Jabsco Color: Black Package Contents: Jabsco 1 1/2" Vented Loop Jabsco 29015-0010: 1/2" Vented Loop