Sewage Treatment - Septic Tanks - FRANCE

Everything that you need to know about Septic Tanks and Sewage Treatment in France.

With the increasing numbers of UK Nationals choosing to buy properties in France, this page is dedicated to helping you through the maze of French sewage legislation.

New Rules as of Jan. 2011

House sellers are now required to have a survey of their septic tank undertaken prior to sale.

This means that if the property has a septic tank, the Contract of Sale must include a diagnostic d'assainissement non collectif.

The report will form part of the Dossier de Diagnostic Technique (DDT) - the House Information Pack of documents that has to be prepared by all sellers.

If a septic tank survey is not carried out, the seller will not be exempt from liability to later defects that may later arise with the operation of the septic tank. They may also be liable for damages.

If the system is later shown not to comply with regulations, then the new owner will be obliged to bring it up to standard.


Septic Tank which takes ONLY toilet waste - no sinks, baths, etc.  Fosse Septique

Septic Tank which takes both toilet waste AND greywater (bath, sink, dishwasher, etc)  Fosse Totes Eaux

Sewage Treatment Plant. Micro-Station

Cesspool which simply stores all the wastewater for regular emptying by tanker  Fosse d'etanche - THESE ARE NOW ILLEGAL IN FRANCE

Greywater (bath, shower, sink, washer, etc)  Eau Usee

Blackwater (toilet)  Eau Vanne

Soakaway  Tranche d'Epandage

Sand Filter  Filtres a sable

The History of septic tanks and sewage treatment in France

In the past, the French separated the grey water (eau usee ) from showers, sinks, washing machine etc and the sewage from the WC (eau vanne) into different systems.

The eau usee ( greywater ) was often piped into a stream or ditch directly without any treatment.

The eau vanne ( toilet waste ) was either:

  • piped into a septic tank ( fosse septique ) with an outlet to a primitive filter bed that normally consisted of a trench filled with stone (tranchee d'epandage)  These septic tanks are usually too small now to cope with the amount of liquid going into them and many are coming to the end of their life anyway.  Please click here for information on septic tank problems
  • or piped into a fosse d'etanche (cesspool) that was supposed to be emptied regularly,

The fosse septiques (septic tanks) are often too small for current regulations.  The fosse d'etanche is usually much larger. Fosse d'etanches were often 'holed' on purpose to reduce emptying costs, but this usually ended in disaster as raw sewage contaminated the groundwater and groundwater filled the tank in winter! 

No septic tank really treats sewage. It merely stores the sewage, separating solids from liquids.  70% of all the original pollutants remain in the septic tank effluent, including bacteria and viruses (such as hepatitis, polio, tetanus, leptospirosis, cholera, para typhoid etc), which are very dangerous if you have not had the required vaccinations.

This septic tank effluent must be treated further and purified by aerobic bacteria in the soil.  This is done via a properly designed and constructed Filter Bed.  This is the part that is missing from most septic systems in France and is the part which you must now have as it is the real treatment for the sewage. It has been estimated that about 80% of  rural French properties do not comply with the new regulations so BEWARE. 

Septic Tank and Sewage System Regulations in France

In December, 2005, everything changed in France regarding Sewage Treatment, when the Mairie of each Commune became directly responsible for every aspect of wastewater treatment.  The Mairie is also responsible for implementing the new strict regulations on Septic Tank systems ( fosse toutes eaux ) and for ensuring the regular maintenance of your septic tank or sewage system, be it an individual (non-collectif) system or municipal ( collectif ).  He/She has to arrange an inspection of your system every 4 years and issue a report, which you must keep.

Areas have been designated either 'collectif' or 'non-collectif' areas.  If an area has been designated a 'collectif' area, it means that a mains sewage system has been decided upon as the best way of dealing with sewage in that area, even if main sewerage is not yet in place.  BEWARE of buying a house in such an area if it does not have existing mains services, as it is unlikely that you will get permission for your own system, or permission to upgrade your own system if it fails the inspection.   You will be forced to connect to the main sewer once it is installed, even if you already have your own fosse septique, as the Law is about Pollution Control.

Because most of the Maires know little about wastewater treatment, they usually appoint a professional body to enforce the law. They are often (but not always) known as S.P.A.N.C. (Service Public d’Assainissement Non Collectif) and will service a group of communes from a local office.

If you already live in France, you will have seen on your water bill a charge  “Redevance Service Public d’Assainissement Non Collectif”. This charge is applied by your water company to help finance the implementation of the law. The cost does vary from region to region.

The main purpose of the Law is to ensure that all the private systems in existence in rural France are fit for the purpose and do not cause pollution of groundwater or watercourses.  They have to be in good condition, the filter bed must be correct, they must work and be maintained correctly and they must be the correct size in order to be able to deal with the amount of wastewater that you produce - an amount which has risen dramatically over the last 20 years!  A visit to your property will be arranged by SPANC and the engineer will verify the :

  • Location of the septic tank
  • Access to and condition of the septic tank
  • Ventilation of the septic tank
  • Volume of the septic tank
  • Sludge level
  • Drain going to the filtration system
  • Nature of the soil
  • Proximity of any water sources, above and underground
  • Filtration system

You will then be given a report that will tell you if your sewage system is working correctly.  It will also explain to you the changes you need to make if it isn't.

Read this before you buy a French property.

If you are thinking about buying a house in France with a septic tank, bear in mind that there are currently extensive projects to connect village properties to mains drainage.

These generally affect homes in the centre of villages, but in any case you should ask at the town hall whether a property is due to be connected to the mains and whether it will be possible to refuse mains connection (provided you have a septic tank system that meets current standards).

 Although mains connection might sound like good news if the idea of having a septic tank in your garden is less than appealing, there’s a slight inconvenience to be taken into consideration – namely cost: there will be a charge for connection to the mains drainage system, which must be paid within two years of connection, plus an expensive annual ‘service’ charge added to your water bill.   

 Properties that aren’t due for connection to the main drainage system will have their tanks inspected in the coming months or years (if they haven’t been inspected already) and thereafter every four years or so to make sure they meet the latest standards, which in many cases will be more exacting than those that applied when the tank was installed. In other words, you could be faced with an expensive bill for a new system.

Note that cesspools are now illegal. You will be given notice of an impending inspection, which is compulsory, and the inspector will draw up a report, indicating any shortcomings of your system. Even if they don’t need replacing, old septic tanks may be in need of drainage, repair, or new pipes, filters or filtration systems. Modern regulations demand, for example, considerably lengthened overflow pipes, which may not be possible within a property’s boundaries.

Individual sewage systems are subject to strict regulations, which are currently in the process of being updated to meet EU standards, and inspections will become routine.

There are essentially two types of septic tank: older tanks (fosse septique) take bathroom waste only, which is allowed to soak into the ground through gravel, while newer tanks (fosse à toutes eaux) take all household waste water and treat it before it’s discharged through a system of drains.

If you need to install a septic tank, you should check the following:

That there’s enough available land, bearing in mind that the drains for a septic tank must be installed a certain minimum distance from the boundaries of a property (e.g. 3 to 5m), and must cover a certain area depending on the size of the tank (generally at least 85m2).

  • Whether there are rivers, canals or other water courses (including underground springs and waterways) that might affect the siting of the tank and soak-away and the type of soak-away – for example, a septic tank mustn’t be less than 35m from a well.
  • Whether the ground is marshy or rocky, in which case installation could be difficult and/or expensive.
  • Whether the land slopes upwards away from the house, which may mean that waste water must be pumped up to the soak-away – another additional expense.
  • Whether there’s access to the site for a lorry (delivering the tank and subsequently emptying it) and a digger to install the soak-away.

The cost of installation for just the septic tank, which can be between €2,000 and €5,000 depending on the size of tank and the type of installation, must be taken into account in your budget. Make sure that a tank is large enough for the property in question, e.g. 2,500 litres for two bedrooms and up to 4,000 litres for five bedrooms. It’s essential to check these things before purchasing a property. 

Your system is also likely to require further treatment before discharge.  The method favoured by SPANC in France is a sand filter, but they are very expensive, large, unsightly and require sand replacement every few years.

One University Study in Poland found that the sand filter allowed less and less effluent to pass through as time went by and one sand filter completely clogged after only 480 days!

The filtration sand is very expensive and what do you do with the old, stinking, contaminated sand?  You can't leave it where children can play in it, the cat can use it as a toilet, etc. or the contamination can cause real problems!

Sewage treatment Plants which discharge direct to a watercourse are much better alternatives to the septic tank/sand filter option.

There are alternatives to septic tanks, e.g. reed beds, but these must be properly designed and constructed to meet the required standards. Bear in mind that the installation of ‘alternative’ sewerage systems may make a property difficult to sell.

You will first have to get a soil percolation test performed on your property in order to be able to determine whether a tranche d'epandage (soakaway) is suitable and if it is, to design it.  Many areas of France are unsuitable.  Your Mairie may be able to give you the name of the local agency that performs the tests, and it is likely to cost several hundred euros if you employ someone to do them.  A septic tank can not be installed without this test being carried out first, since the test will enable the authorities to tell you what size and type of sewage system you need in order to comply with the regulations.

The most common type of existing septic tank comprises of a tank, buried in the ground, that collects all toilet waste from the property, and then releases it through underground pipes bedded in stone, into the surrounding area. Typically 20 - 50 metres of buried pipe were installed.

It depends on how absorbent your soil type is, but you should be aware your existing soakaway is unlikely to comply with the new regulations. Unless your soil is very absorbent sandy or silty loam with a depth of at least 1 metre below the pipe, then a different method of treatment will be required.  Discharge of septic effluent to a watercourse is illegal.  The most common system for septic tank effluent treatment is a sand filter, which involves a very large hole being dug, perhaps 30 square metres and 1.5 metres deep, lined with heavy duty plastic, then filled with various layers of sand, gravel, and geotextile membranes. The outflow from the septic tank (which has received ALL waste water from the house, not just toilet waste) then passes into this filtration system, through pipes spread across the top, filters through the sand bed, and is collected by further pipes at the bottom before being released into the environment. As you can imagine, this may take up a very large part of your garden and many properties sold in France do not have enough land to install one anyway!

Documentation Requirements

All recent septic tank installations should have been documented and the records placed with the Mairie.

If you are purchasing an old house in the country ask to see the legal certificate of approved drainage - It is unlikely that there is one and it is YOUR responsibility to obtain it. This is usually a BIG problem, as most old houses do not have a sewage system which will pass. The notary will need it before you can resell the property in the future.

Your Mairie will decide whether or not a new fosse toutes eaux or mains drainage connection is required.


For new build and to replace an existing septic tank, you will have to go to your Marie and ask for an application form - "Demande d'installation d'un dispoitif d'assainissement non collectif"

The application requires:

  • The application form completed and signed - including number of main rooms, slope of the land, the ground water level and the type and size of filter bed.
  • A location plan (1:25,000 or 1:10,000)
  • A layout plan showing existing and future buildings, the proposed location of the septic tank installation, any wells or streams and the slope and direction of slope of the land.

Septic Tank Installation Costs

The size of the septic tank ( Fosse toutes eaux )  installations depends on the number of main rooms as the septic tank is sized as follows-

Number of main rooms ( bedrooms + 2)          Septic Tank size in cubic metres

5 and under                                                                            3

every additional room                                      one extra cubic metre per room 

Septic tanks vary in cost, but the cheapest one is likely to cost around 450 to 1000 euros

The pipework and fittings between the house septic tank and septic tank to filter bed will also cost several hundred euros. Additional drainage runs can add a day to the programme and increase the cost by up to 1000 euros.

The cost of the filter bed materials bed will be approximately 35 euros per square metre.

A straightforward installation for a 5 main room residence will take about 4 to 5 days - this could increase to 7 for a large complex installation. A team of builders with their plant and equipment will cost about 1000 euros per day.

If you require the spoil to be removed off-site, then expect to pay about another 1000 Euros. 

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. 

Septic Tank ongoing Control by the Mairie in France

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. For example, you need to check the sludge level, and if the tank becomes over 60% full with sludge, it must be emptied and re-started, or partially emptied. It is probably better to partially empty the tank if action is required, as if the tank is completely emptied of solids it will begin to cause a smell unless it is correctly re-started. The water levels and scum layers should also be checked. If a pump out is required, you must use a registered and approved company (your Mairie will advise)  You need to retain your receipt to show to the inspector at the four yearly check.

Rules on minimum distances for septic tanks in France

You cannot site a septic tank within three metres of a neighbouring property. It is also forbidden to place a septic tank less than three metres away from trees and shrubs, although smaller garden plants may be exempt from this rule. Despite its name of fosse toutes eaux, rain water must in no circumstances get into the septic tank, so make sure that there is an adequate alternative drainage system for this. Other rules state that you must leave thirty five metres distance between the filter bed of the septic tank and a water source, such as a stream or well. Obviously ventilation is important, and easy access by safely covered manholes is also a must have. It is only necessary to install a fat trap or grease trap if the septic tank is more than ten metres away from the kitchen. If this is called for, try to place it as close to the property as you can.


If you are having trouble with SPANC not approving your chosen sewage system and insisting on a sand filter, download this file which gives the minutes of the Senate Amendment requiring certain CE certified plants to be accepted and sand filters to be banned!  SPANC are behind the times as far as legislation is concerned. It is in both French (to show to SPANC) and English translation.

There is now an approved sewage plant list for France.  Note that most UK made plants are NOT on the list, though some are actively marketed in France.  This could cause problems with SPANC as there are minimum capacities for tanks in the new French Regulations - 2500 litres for 6 person extended aeration units (like WPL Diamond) and 2500 litres per chamber for 6 person separate chamber systems and they may not be large enough.  Check and find out before you buy! We wait and see what develops.

You are only allowed to install plants that are on the French Government Approved List. The EN12566-3 Test was supposed to be a ‘Harmonised Standard’ throughout the European Union. However, France changed the goalposts and decided to have its own standard which is the FR EN 12566-3. The overloading part of the test went up from 150% to 200%, they insisted on a minimum 300mg/L BOD on the influent sewage received by the plant, they introduced a ‘Le Weekend Cottage’ part of the test where plants were fully loaded for 2 days and no loading for 5 days. France also put minimum volumes on all chambers in the plants. This means that most UK plants sold in France are NOT THE SAME as the ones sold in the UK and are not accepted by the French Authorities! Many people have bought plants in the UK that are on the French List, (because they are a lot cheaper to buy here)only to find that they are not allowed to install them in France as they are not the French version. Often, UK dealers will not tell you this when you buy them! The Vortex is currently undergoing the French EN 12566-3 test, but it will not be ready for sale there for another 12 months, and, like the others, the tank size is different to the Vortex plants sold in the UK. To sum it up, in order to be safe, you should buy a sewage plant in FRANCE, as this will then be to French standards. Do not import one from the UK as you may find yourself with a useless plant!

Non-electric sewage treatment systems qualify for a 0% interest ECO LOAN.

A recent government action has created an ECO LOAN scheme at 0% interest, to finance improvements to the energy performance of dwellings completed before 1 January 1990 for use as a primary residence.  This ECO LOAN scheme covers sewerage upgrades for up to 10,000 Euros, only where Non-Electric sewage systems are installed.