Landheer WaterinnovatieToo small is unfavourable, too large is expensive and unnecessary. This is how you calculate the right tank size for your home.
The basic principle
The ideal tank size depends on two factors: how much rainwater can be collected per year (roof area), and how much of it you will use per year (applications + residents). In general: your tank should be able to buffer about 5% of the annual collection, to bridge dry periods.
Calculation examples
An average house with an 80 m² roof in the Netherlands collects around 64,000 litres of rainwater annually. For a family of 4 that uses rainwater for toilet and washing machine, 4,000 to 6,000 litres is ideal. For larger homes (120+ m² roof), heavier use or drinking-water applications you scale up to 10,000 litres or more.
Off-the-grid: calculate more generously
For off-the-grid applications (such as the Caroline project) the tank is calculated more generously: at least 8 weeks of full buffer, often 15,000 to 30,000 litres. In addition, a second filtration line is needed for drinking-water quality. During the consultation we calculate the exact size.