The usage was so huge that we doubted our meters when someone said it's not a leak but a faulty meter. A daily use of 5000 liters in a house is truly not normal, and we were not able to identify a leak easily. Finally, a flush leak was identified and stopped in a basement toilet (hence it wasn't noticed) and usage dropped 78%. A few more investigations and plugs and a further 7% drop later the usage became on par with a regular urban villa.