PATH’s Safe Water Project is implementing innovative methods to enable commercial enterprises to produce, distribute, sell, and maintain effective household water treatment and safe storage (HWTS) products for low-income populations in multiple developing countries around the world. This project brief summarizes PATH's product development process to design an HWTS device that specifically meets the needs of low- and middle-income families. This brief also describes PATH's efforts to create a set of design guidelines for HWTS devices.