Open-Source Water Testing Kit

Before you purify it, you need to know what's in it. Bengaluru's borewell and lake water quality is all over the map. Need an affordable, open-source testing kit that measures TDS, pH, turbidity, and dissolved oxygen, with probes for common contaminants like nitrates and hardness. ESP32 data logger, a phone app for results, and an opt-in public water-quality map. Off-the-shelf sensor probes, full BOM under ₹5,000, all designs open.