The increasing demand for sustainable and decentralized water treatment solutions has highlighted the need for low-cost filtration systems capable of treating alternative water sources such as rainwater and greywater. This study proposes the design of an innovative multi-stage filtration system that integrates natural filtration materials with selective functional enhancements to improve water purification efficiency. The proposed system consists of sequential layers of gravel, coarse sand, fine sand, TiO₂-coated sand, and zeolite, supported by a cotton separation layer and followed by a ceramic candle microfilter and copper mesh outlet. Natural materials provide mechanical filtration, adsorption, and ion exchange, while the TiO₂-coated sand introduces photocatalytic degradation of organic contaminants. The system is designed as a gravity-driven prototype suitable for small-scale and decentralized applications. By combining conventional natural filtration media with advanced functional materials, the proposed filter aims to enhance turbidity removal, chemical adsorption, and microbial reduction while maintaining affordability and environmental sustainability. The concept demonstrates the potential of hybrid natural–engineered filtration systems as practical solutions for potable and non-potable water treatment in resource-limited environments.