Coin Volcano

🏠 A roof is a catchment surface with a number attached to it. Coin Volcano 🌧️ works out that number and then runs a year through it.

📐 Enter your roof as the planes it is actually made of south pitch, north pitch, garage, porch, shed: each with its own dimensions 📏 material 🏗️ and runoff coefficient. Metal sheds water differently from shingle and polycarbonate differently again, so the effective area is always smaller than the measured area. Photograph the roof and mark the planes directly on the picture when it's easier to point than describe. The photo stays on your device 🔒 and can be removed anytime.

📅 The Year Board is the heart of the app. Twelve monthly cells show rainfall 🌦️ harvested water 🚰 household usage 🚿 and the final tank level. The reservoir model calculates harvest, overflow 🌊 mains top-up 🚰 and dry days. Open any month in Coin Volcano to see every detail: litres in, litres out, overflow, deficit and days the tank ran dry.

🛢️ Tank sizing is fully interactive. Drag the capacity slider 🎚️ and the entire year recalculates in real time, letting you compare five tank sizes side by side 📊 and easily spot the point of diminishing returns.

🚿 Household demand is built from six water-use categories, each with customizable litres, frequency and seasonal weighting 🌱 Rainfall uses six editable climate profiles 🌍 nothing is downloaded or guessed.

📚 A built-in guide explains first-flush diverters, gutter sizing, mesh grades, tank materials, overflow routing and maintenance. Everything works offline in Coin Volcano 📴 and stays on your device.

Recent changes:
fixed all bugs