The water detection sensor includes a retrofit system such as a water-proof housing that selectively attaches to an exterior of a water conduit coupled at or near a dispense outlet of an emergency safety shower or emergency eyewash unit. The sensor may include a pair of guidewires that extend through the body of the water conduit and have a pair of respective electrodes that reside therein in non-conductive relation during an “off” or “no flow” condition. In an “on” or “flow” condition, the electrodes become immersed in water and can conduct electricity therebetween by way of the electrically conductive water medium. As such, a water conductivity circuit coupled thereto and disposed within the water-proof housing may relay a signal to a controller, which activates an audible or visual alarm that water is flowing through the emergency safety shower and/or the emergency eyewash unit.
