Summary This project details an open source water testing platform derived from the open-source colorimeter, which is made from open source electronics and 3-D printable components. This is part of a larger project to reduce the cost of scientific equipment using open-source hardware. For full BOM, OpenSCAD, and details go here. For technical details read the paper here: Bas Wijnen, G. C. Anzalone and Joshua M. Pearce, Open-source mobile water quality testing platform. Journal of Water, Sanitation and Hygiene for Development, 4(3) pp. 532–537 (2014). doi:10.2166/washdev.2014.137 open access