This disclosure provides a fuel system for supplying fuel to an internal combustion engine, an internal combustion engine that includes such a fuel system, a connector for connecting a single-walled high pressure common rail to a double-walled fuel line segment, and a fluid containment system. Each embodiment includes drain plumbing having a leakage drain connector that can be used to provide an interface between a single-walled high pressure common rail and a double-walled high pressure fuel line segment, and also provide part of a low pressure passage fluidly connected with a low pressure passage of the double-walled high pressure fuel line segment. The drain plumbing also can provide an interface with a low pressure fuel drain line fluidly coupled to a leakage detector.