The use of rainwater is fairly easy to realize. Most homes in Europe and beyond have a roof drainage system in place. However, for decades the only concern was to get rid of the water as soon as possible. Nowadays, we think twice about it. The recovery and storage of rainwater for a separate use in a household has become a substantial cost saving exercise. In the Paris region in France you can expect on average 650 liters of rainwater per year per square meter. For a roof size of, for example, 70 m2 this yields about 45.000 liters per year. If you take a shower using 40 liters this allows you and your household to take 1125 showers or 3 persons almost one shower every day. Average household consumption in Paris is 120L/day, which adds up to about 44.000 liters per year for washing and toilet use. On a monthly basis with a storage capacity of 4000 liters of rainwater per adult person you should be able to manage your own consumption with your own roof drainage system. It is a rather simple use case. Maybe during dry summer months the calculation is a bit too optimistic, but the potential for a water autonomy of households in Europe is an option. In addition to the dry January, the no mow May, we shall have the no shower July next.
