Small units on urban combat missions carry a limited volume of water in their hydration packs or in bottles. On many occasions, troops encounter local water sources such as water tanks on roofs and water from wells which can be easily contaminated with chemical or biological hazards. “Spring” is a small, man-portable water purification unit that fits into a backpack and can filter water to the required hydration needs of a squad or platoon. The unit produces fresh, pure water from any indigenous water source, e.g., tap water from a captured building, water tanks on roofs, wells, etc. The device is small and light-weight, and reduces the logistical need to supply large amounts of water to troops during operations.