Finding the drainage plans of a house is not just about rummaging through a construction file. Between public networks registered at the single window and private pipelines that no one keeps track of, the process involves several documentary sources and often, a supplementary site survey.
Internal private networks: the blind spot of drainage plans
Pipelines located within a fenced property and operated by the owner are not subject to registration at the single window for networks. In practice, internal private networks escape the national tele-service. Neither the municipality nor the operators have their layout.
This documentary gap concerns wastewater evacuations between the house and the connection chamber, buried rainwater collectors in the garden, and empty conduits laid in anticipation for fiber or irrigation. For these networks, the only reliable source remains the construction permit plan, the installer’s file, or a physical survey on site.
We recommend creating a technical file upon receipt of the works, with measurements in plan and depth, and systematically attaching it to the sales deed. Without this document, any buyer starts from scratch. A detailed methodological guide is available on the La Bonne Maison website to structure this documentary research.
DT-DICT and single window: leveraging public network data
For public networks crossing or bordering your plot, the entry point is the tele-service of the single window (reseaux-et-canalisations.ineris.fr). Any project work declaration (DT) or declaration of intent to commence work (DICT) is submitted there, and operators must return the plans of their works with a defined precision class.
The anti-damage reform resulting from the law of July 12, 2010 and the decree of February 15, 2012 requires these declarations even from individuals. As soon as you use a machine or mechanical tool on land crossed by a public network, the DT-DICT applies. Digging a trench for a hedge without prior declaration can lead to a fifth-class fine and full responsibility for repairs.
The procedure occurs in two stages:
- The DT (project work declaration) is sent during the design phase. It allows obtaining the plans of existing networks within the construction site.
- The DICT (declaration of intent to commence work) is sent before the actual start. It triggers the marking and staking on site by the concerned operators.
- The receipts from the operators specify the precision class of the cartographic data (A, B, or C), which directly conditions the excavation techniques allowed nearby.
A network classified in precision C (uncertainty greater than one meter fifty) requires additional investigations before any mechanized excavation. We observe that the majority of municipal sanitation networks in rural areas remain in class B or C, making the operator’s plan insufficient on its own.
Cadastral plans and municipal archives: what you really find there
The urban planning department of the municipality keeps building permit files, which should include the mass plan with the layout of the drainage networks. In practice, files prior to the 1990s are rarely digitized and sometimes incomplete.
The public sanitation network plan (collective or rainwater) falls under the sanitation service of the municipality or the intercommunal body. This document indicates the layout of public collectors and the location of connection chambers at the property boundary, but not the routing of private pipelines between the chamber and the house.
For recent constructions, the sanitation compliance file (issued by the SPANC for non-collective sanitation or by the municipal service for collective) constitutes a more reliable source than the initial mass plan. It incorporates modifications made during the construction.
Sanitation file and real estate sale
Since the establishment of the mandatory sanitation diagnosis for sales, the seller must provide a status of the installation. This document does not always contain a scaled plan, but it mentions the type of connection and notes any non-conformities. The absence of a scaled plan in the diagnosis is not a reason for nullity of the sale, but it weakens the seller’s position in case of post-acquisition disputes.
Site survey by camera inspection and ground-penetrating radar: when plans are missing
When no document allows for the certain location of the pipelines, a physical survey remains the solution. Two techniques dominate in residential contexts.
Endoscopic camera inspection involves inserting a camera head into the network from an accessible chamber. The operator identifies the linear path, connections, slopes, and anomalies (back slopes, roots, crushes). An integrated probe transmitter in the camera head allows for locating the pipeline from the surface with a receiver and mapping the layout.
Ground-penetrating radar scans the surface terrain and detects discontinuities in the soil, including non-metallic pipelines (PVC, sandstone, concrete). This technique is particularly useful when chambers are inaccessible or when networks have been laid without apparent connections.
- Camera inspection provides a diagnosis of the internal condition of the network in addition to its location.
- Ground-penetrating radar covers a wide area and also detects empty conduits and abandoned networks.
- The combination of both methods produces a reliable as-built plan with measurements in X, Y, and depth.
We recommend systematically requesting a deliverable in a georeferenced digital format (DWG or shapefile), reusable by a surveyor or an engineering office. A paper plan without coordinates loses all value as soon as the land layout is modified.
The obtained layout should be archived with the property documents and transmitted during any resale. This is the only way to break the cycle where each successive owner starts from scratch, due to a lack of exploitable data on their own pipelines.
