Warning over impact of sewerage systems on property prices in France

The state of a property’s drains can directly affect the value of a property and its successful sale- especially if they are not linked to a communal sewer system - an agency working with France’s notaires has warned.

Properties with sub-standard sewerage systems can be sold with an official certificate of non-conformity, but remedial work will have to be done within two years of purchase and, as a result, sales prices will be lower.

Rules on drains have evolved considerably in France over the last 20 years. It is now obligatory to have an approved drainage system in place, either into collective sewers or an individual system (assainissement non collectif).

The most common individual system is a fosse toutes eaux, sometimes loosely referred to as a fosse septique, an older system that only treated toilet (black) water.

There are alternatives, however. These are generally more expensive and require electricity to power pumps, often producing cleaner treated water and occupying less space in a garden.

Five million homes have individual drainage systems

“Individual drainage schemes are often seen as a technical subject but they are important aspects in terms of a property’s value and perceived quality,” said Nathalie Duny of Notariat Services.

“Notaires must make sure the information is clear and accurate.”

Around five million French homes have individual drainage systems, mainly in rural areas.

When a commune has collective drainage, it is usually compulsory for all properties to join this system, with a charge added to the annual taxe foncière to help pay for it.

All sewerage systems in France must now be able to collect wastewater from toilets (eaux vannes) and from kitchens, baths, showers and washing machines (eaux grises).

After treatment, they must ensure the water can be returned to the soil without causing environmental damage.

In what are now called “traditional systems” (although the tradition is only 20 years old), a tank collects water from the drains and neutralises toxins through the action of bacteria. The process is completed by sending the water through a downstream drainage system and into the soil.

Once installed, the advantages of this system are that it is usually long-lasting and robust (as long as heavy vehicles do not drive over it), it works without electricity and has low maintenance costs.

Associated costs are usually limited to emptying the collection tank every four years, and paying for inspections from the local Service Public d'Assainissement Non Collectif (SPANC) every 10 years. Fees for the latter vary from commune to commune.

Notaires put the price of a “traditional” installation at between €6,000 and €10,000, and they say most occupy between 80m² and 120m² of land. A five-metre perimeter around the tank and drains must be cleared of trees.

Traditional systems are not suitable where a property does not have a large enough garden, if the land slopes too steeply, or if the soil is very impermeable.

Alternative systems

Three main alternative systems have been approved in France: micro purification stations (microstation d'épuration), filter systems based on coconut fibres, zeolite rock or sand, and reed beds.

A French firm called Innoclair has become a European leader in micro purification stations.

Their plastic tanks are designed to be installed vertically, with electric stirrers and pumps built in.

The stirrers agitate the sludge which gathers at the bottom of the tank, allowing a quicker and more complete treatment, to the extent that treated water can be safely used to water gardens.

Filter systems pump water from the tank through filters to remove solids. They sometimes have another treatment tank before draining into the soil.

In reed bed systems, the wastewater enters a shallow bed filled with gravel or sand and planted with reeds. Microorganisms living around the roots break down organic waste, while the gravel filters particles.

Using treated water from reed beds is not advised for vegetables, but it is fine for flowers and trees.

Notaires put the prices of alternative systems at between €8,000 and €12,000 and they require between 5m² and 20m² of space.

They generally need more maintenance than traditional systems, especially to clean filters and screens, and may have to be emptied more frequently. Annual costs are estimated at between €100 and €200 a year, compared to €60 to €100 for a traditional fosse toutes eaux.

SPANC technicians must sign off all installations, usually after the equipment has been installed but before the area is backfilled.

They must also provide a new certificate of conformity – for a fee – when houses are sold. The certificate and report are included in the sales documents prepared by notaires.

Grants for replacing a septic tank are available, as well as interest-free eco loans (éco-prêt à taux zéro). More information can be found here.