Abstract: An ultra-compact combination exhaust muffler and aftertreatment element and water trap assembly provides exhaust flow through an aftertreatment element surrounded by an annular water collection space receiving water diverted and shed from an upper dome cap above the aftertreatment element and below the upper outlet. In a further embodiment, the assembly includes housing sections separable from each other at a service joint axially between axial ends of the aftertreatment element for ease of servicing. In a further aspect, the aftertreatment element has an axial end within a housing section saving axial extension space.