Huanyu Chen¹ and Jonathan Sahagun², ¹China, ²California State University, USA

Freshwater scarcity and the under-utilization of household rainwater harvesting motivate the need for accessible water monitoring tools. This paper presents Storm Vault, an integrated IoT system that pairs a low-cost ESP32-S3 sensor module with a Flutter mobile application to provide real-time visibility into rain barrel water level and quality. The hardware uses a VL53L4CD time-of-flight sensor and an analog turbidity sensor read through an ADS1015 converter, transmitting readings every thirty seconds over Wi-Fi to a Firebase Realtime Database. The mobile application authenticates users, lets them register barrels by device identifier, and displays live circular gauges, water-quality classifications, and historical line charts. Validation experiments showed that distance measurements were accurate to within 1.5 cm and that turbidity classification was reliable except for samples sitting near a category boundary. By making rainwater harvesting tangible and easy to monitor, StormVault encourages consistent use and contributes to responsible household water consumption.

Rainwater Harvesting, IoT Monitoring, Time-of-Flight Sensing, Turbidity Detection, Firebase Realtime Database, Flutter, ESP32, Environmental Sensing