fosse septique maintenance costs

A house for sale has no main drains available and an official inspection demands the installation of a grease trap. 

Assuming a new grease trap is installed and the rest of the fosse system is in good order please can anyone tell me what sort of running costs are involved year on year. 

Paul

We've been in our last house and this one for seven years each time and have never had to have anything done to either fosse although they were both put in new when we moved in. The grease trap needs cleaning out every couple of years, but my husband does this himself. So basically running costs are nothing apart from the odd time I buy the cleaner to put down the toilet (the name of which escapes me at the moment) but most of the time I chuck out of date yoghurts down.

Some communes clean out the fosse for you free of charge as part of their services. Ask the mairie. If you need to get it done privately, it will cost approx. Euro 150 - 200 every 3 to 5 years depending on the size of the tank, etc.

Our Fosse Septique was cleaned out for 70 euro last year, but the man
only does local to Salon la Tour. Our friend up the road paid 200 euro
for a company to do the work as they were unaware of the local man.

We've had our fosse for 10 years now and still haven't need to have it emptied. We chuck a powder down the tiolet once a week and only use non-aggressive cleaning agents.