Question: how much does it cost to install a septic tank in france?
Answer: In short, the cost of installing a Fosse toutes eaux is around 6000 to 7000 Euros for a 5 roomed house with at least an extra 1000 euros for every additional room. Your fosse will be inspected by the Mairie every four years, but during this time you should check it regularly and take any necessary action.