The invention generally provides a system and method for detecting, measuring, and/or classifying particulate and/or water contaminants in a fluid supply line, storage tank, or sump. Embodiments of the invention provide a contaminant detection apparatus with a detection chamber and a detection module. The detection chamber includes a housing with an internal fluid conduit and one or more acoustic transducers disposed in the housing. Alarms and/or automatic signaling may be included to shut off valves or pumps when contaminants are detected.