The collective sewage network plan is not a standardized document at the national level. Each community manages its own archives, with varying levels of precision and access conditions. Finding a sewer plan requires distinguishing between several types of technical documents that do not have the same legal value or cartographic reliability.
Sewage zoning plan and as-built plan: two documents not to be confused
We regularly observe confusion between the sewage zoning plan and the as-built plan. The former delineates areas subject to collective or non-collective sewage treatment within the municipal territory. It is generally included as an annex to the local urban planning plan (PLU) and can be consulted at the town hall or on the urban planning geoportal.
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The as-built plan, on the other hand, documents the actual layout of the pipelines as installed by the construction company. It is the only document that precisely locates connections in private domains. The community’s sewage service archives it after the completion of the work. To better understand how to find a sewer plan, it is useful to know which type of document corresponds to your situation.
The problem: for older installations or those never regularized, this document simply does not exist. The FNCCR reports in its 2023 report on the heritage knowledge of networks that many connections remain “orphaned,” without available as-built documentation. The absence of as-built documentation mainly concerns connections made before the 1990s, a time when systematic archiving was not the norm.
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Open data of sewage networks: what SIG portals really show
Since 2023-2024, several metropolitan areas have been publishing georeferenced sewage network plans as open data. Paris, Lyon, Nantes, and Montpellier offer datasets in SIG format that can be freely consulted.
However, this data is deliberately degraded. The exact depths of the collectors and certain sensitive sections are obscured for security and anti-intrusion reasons. A plan from Paris Data or data.grandlyon.com provides the layout in plan view, not the longitudinal profile or the invert levels.
For a connection or excavation project near the network, this open data does not replace a direct consultation with the network manager. However, it allows for a quick check to see if a parcel is located in a serviced area and to identify the nearest main collector.
Concrete limits for a diagnosis or sale
During a real estate sale, the sewage diagnosis must attest to the compliance of the connection. A degraded SIG plan is not sufficient to document the state of the private connection. The sewage diagnosis relies on a physical inspection, not on a cartographic plan.
We recommend not to confuse public geographic information (approximate layout of the network) with technical proof of the connection (as-built documentation or diagnostic report). The notary will require the latter, not the former.
Obtaining the pipeline plan from the sewage manager
The most reliable approach remains a direct request to the public collective sewage service (SPAC) or the delegate. Procedures vary by community:
- Some municipalities handle requests by mail or online form, with a response time of several weeks. The town hall directs to the appropriate contact (municipal management, inter-municipal union, or private operator).
- Others limit consultation to authorized professionals (engineering firms, commissioned excavation companies). The individual must then go through a service provider to obtain the information.
- In metropolitan areas with a SIG portal, free access downloading eliminates the need for a formal request, but with the precision reservations mentioned above.
The first reflex is to contact the town hall to identify the network manager for the concerned parcel. The site monbranchement.fr, a public service for residents of Île-de-France, offers an interactive map that directly displays the contact details of the manager based on the address.
Cases of unconnected parcels or in development zones
For a construction site, the network plan allows for sizing the connection and estimating the trench length between the property boundary and the collector. If the parcel is not yet serviced, it is the sewage zoning plan that indicates whether a future connection is planned or if the installation falls under non-collective sewage treatment (septic tank).
The urban planning certificate (CU) mentions the existence or non-existence of the collective sewage network nearby. This document, issued by the town hall, serves as a reliable starting point before any building permit request.
Searching for buried pipelines: when the plan does not exist
In the absence of archived as-built documentation, the physical location of the pipelines becomes the only option. Two methods are common in the field:
- Electromagnetic detection allows for the identification of metallic pipelines or networks equipped with warning mesh. A specialized technician surveys the parcel with a detector and maps the layout.
- Camera inspection (passing a camera through the pipeline from a manhole) identifies the exact path of the connection, its condition, its connections, and any anomalies (back slopes, infiltrations, cross connections).
- The topographic survey of existing manholes, combined with the cadastral plan, allows for reconstructing a probable layout between visible access points.
These interventions represent a significant cost, but they produce a usable document for work or to regularize a non-compliant connection. A camera passage remains the most reliable means of mapping an old private connection.
For a renovation project or a real estate transaction, cross-referencing the zoning plan of the PLU, the available open data, and a physical inspection of the connection provides a complete view of the connection. None of these sources, taken in isolation, covers all the necessary information.