What is the ‘soil survey’ required before fitting a septic tank in France?
Local authorities may ask for an étude de sol before you install a new sanitation system that is not connected to sewers
The type of septic tank you can fit often depends on drainage, space and the lay of the land
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Reader Question: I need to install a septic tank in the property I wish to buy, but have been told I need to do a soil survey beforehand. What is this, and how do I get one?
An étude de sol (soil survey) is required by some communes before installing an individual sanitation system, such as a septic tank, on property that is not connected to the public sewerage system
The survey assesses various factors including the ground’s drainage and permeability and the presence of rocks.
It also reviews how much work will be needed to fit an individual sanitation system.
An étude de sol is not to be confused with an analyse de sol, which is an in-depth analysis of the composition of the soil.
A soil survey can last between two and six weeks and must be performed by qualified professionals, who visit your property, take samples and fit diagnostic equipment, which they leave in place for the duration of the survey.
The typical cost is between €400 and €2,000, depending on system size, the land, environmental factors and your local area.
Read more: What are the rules to install a septic tank in French holiday home?
Is it mandatory?
There is no generalised national law requiring soil surveys before installing a new system.
However, communes are free to impose this requirement via the local Service Public d’Assainissement Non Collectif (known as a SPANC).
You need to apply to your commune’s SPANC prior to fitting a septic tank or equivalent individual sanitation system.
It will inform you if you need to carry out a soil survey before installing a new system.
Note that you cannot obtain a building permit for a septic tank or equivalent from the mairie without SPANC approval, making the soil survey mandatory in some areas.
Nonetheless, the survey can provide information that helps inform your choice of septic tank, potentially saving you money in some cases.
The local SPANC will be able to inform you of local professionals in your area who can perform the survey.
In some communes the SPANC may be able to do the survey itself.
Alternatively, professionals are available online by searching for étude de sol pour assainissement individuel.
Read more: Explainer: the rules around septic tanks in rural France
