South West France Fosse

Waste Water Treatment
The Facts

It is widely known, that virtually all rural French properties have non-conforming Fosses. Owners are obliged to rectify this and modify or install a system that meets the prevailing regulations. However knowing which system to choose is often confusing. Capital costs, running costs and sustainability are some of the many factors to be considered.

Most property owners are unaware that there are better alternatives to the traditional system of the fosse tank and sand filter.  Micro stations and Compact filters provide an Ecological and sustainable solution for almost all applications.

How do they work?

micro station charente

Micro Stations biologically treat the dirty water with naturally occurring bacteria which feed on the waste and clean the water.

The process has three stages -
Primary separation, where the solids settle to the base of the tank and anaerobic breakdown begins. The water passes to the Bio-reactor chamber, where a fixed bed of bacteria, sustained by a continuous supply of air, digest the impurities. The water finally passes into the secondary settlement chamber before being discharged as treated water.

Compact Filters work in a similar way using bacteria to breakdown the impurities in the water. In the compact filter there are normally two chambers. The primary settlement and treatment sections. The action in the primary section is the same, in the treatment chamber the dirty water passes through a filter media that “holds” the bacteria and after passing through the media the water is discharged having been treated.



A major advantage of both the Micro Station and Compact filter are the known “Future costs”- de-sludging/running costs. Both will have the same periods for de-sludging – between 2-3 years depending on occupancy.

- The micro station will use approx €40-50 per year in electricity for the pump but has no further costs.
- The compact filter media will require replacement after approx 15 years at a cost of between €500-€1,500. Any maintenance can be carried out by yourself.

Whereas for the traditional Fosse and sand filter, the current consensus of opinion is that the sand filters will need replacing after 10-15 years at a current cost of approx €10,000 making it considerably more expensive in the long term.



The cost for the installation can only be determined after a survey has been carried out, however below is an estimate for a typical 4 bedroom house.

Traditional fosse and sand filter: €7,000-8,000
Micro Station: €8,000-9,000
Compact Filter: €8,500-10,000
All prices are plus TVA @10% and current as of Jan 2021.


Service Public d’Assainissement Non Collectif – This is the body who have the responsibility for the regulation of sewage treatment. They can be private companies engaged by several communes or they are a department within the commune itself, but in all situations they have two missions. The first is to inspect and determine whether existing systems conform and the other is to verify that new installations are in accordance with the current regulations.

It is a common misconception that SPANC have the authority to insist that one particular system can be used over another. They can advise but it is up to the owner of the property and their designer to make the decision on the system to be used.
All installations do need the approval of the SPANC office before work can commence and some offices will require an “ETUDE”.

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insured by lloyds

All work complies with current French regulations 
10 Year Decennale Insurance
Mobile: 06 04 14 84 86 
Siret number: 823 420 708 00013