Learn how to design and build your own domestic sized water tank to collect, store and use rainwater for your home and garden. Save money on this low cost method of construction and reduce your water bills too! The combination of cheap, easily available materials, margin for error, suitability for amateurs and flexibility in terms of size and shape, make ferrocement tanks an ideal choice for anyone looking for long-term water security on a budget, and they work well in all but the harshest environment. With hands-on experience, the authors provide a detailed guide to enable confident and safe construction by anyone interested in building their own ferrocement tank. Felicity and Daniel share their reasons for choosing these tanks, how they calculated their water needs and how they constructed and maintain their tanks that cater for all their needs. With our weather patterns drastically shifting between drought and flood due to the climate change, it is vital to have reserves of water to rely on. Felicity and Daniel self-built their own house and included water tanks. They achieved water security for less than the cost of joining the local water network! Whether you are creating your own off-grid home, or want to reduce your carbon footprint and reliance on mains water, the ferrocement tank offers a simple, achievable and robust DIY solution. AUTHORS: Felicity Lee and Daniel Coleman live in a self built, off-grid strawbale house on 2.8 acres in France. They self built their ferrocement water tanks and offer an online consultation service for those exploring the option. They share their off-grid journey at https://lesvignesbasses.org. Colour illustrations