Harvested rainwater is not initially potable. Even after first-flush diversion, it may contain suspended sediment, organic matter, bacteria, and trace contaminants from the roof surface. A multi-stage filtration system is required to render it safe for drinking and cooking.

The standard Pangea filtration train begins with a spin-down sediment trap at the inlet to the cistern, which removes large particles. Water from the cistern passes through a sediment filter (typically 5-micron) to remove fine particles, then through an activated carbon block filter to remove dissolved organic compounds, chlorine derivatives, and taste/odor compounds. The final stage is a UV sterilization unit or ceramic filter that provides microbial treatment, rendering the water safe for drinking. This system is compact, maintainable by non-specialists, and produces water of high quality. The Water Organizing Module (WOM) packages these components into a single organized assembly that is easy to install and service.