When preparing an extension, whether to lay a terrace or simply to seal a suspected leak in the garden, the first question arises: where do the pipes run? Without a reliable plan at hand, even the slightest shovel strike becomes a gamble. Finding the pipe map of your house requires searching in the right places, distinguishing between what belongs to the public network and what remains strictly private.
Public network and private connection: a boundary that varies by municipality
Before digging through archives, one must understand a distinction that many homeowners overlook. The public sanitation network ends somewhere between the roadway and the plot, but this “somewhere” is not the same everywhere in France.
The boundary between the public network and private installation depends on the local water service regulations. It is the municipality or intermunicipality that defines the responsibilities. Specifically, the public network plan does not show the private connection to the house. For this section, one must look elsewhere: construction files, documents from the installer, or site surveys.
This distinction has a direct impact on the procedures. If you are looking to locate the drinking water pipe that crosses the sidewalk, you should contact the municipal water service. If you want to know where the drainage runs between the kitchen and the inspection chamber in the garden, you need to search the private archives of the building. Therefore, finding the pipe map of the house requires conducting two parallel searches, one public and one private.
Single window for networks: what it provides and what it does not
The online service “networks and pipelines” (reseaux-et-canalisations.ineris.fr) is the first logical reflex. Created under the Grenelle 2 law, this single window lists network operators (gas, electricity, water, telecommunications) and allows you to identify which operators have installations near a plot.
You submit a project declaration (DT) or a declaration of intent to start work (DICT) to obtain information from the relevant operators. Each contacted operator then sends back their network plans.
The catch: the single window does not provide the complete layout of private pipelines. It lists the networks declared by the operators. The pipes within the plot, those laid by a contractor during construction or renovation, may be completely absent from this mapping. Thus, you get a partial view, useful for public networks but insufficient for knowing the exact routing under your own house.
When the DT-DICT becomes mandatory
For any construction project involving excavations or penetrations into the ground (even a simple fence with sealed posts), regulations require consulting the single window. Construction professionals know this, but individuals doing their own work often forget. This can lead to accidentally piercing a gas line or a water pipe without any prior mapping.
Private pipeline plans: where to search in building archives
This is the most laborious part. Private pipelines (wastewater drainage, rainwater, cold/hot water supply, possibly rainwater recovery) are not listed in any centralized database. You must piece together the puzzle from several sources:
- The building permit and site plan submitted to the town hall. The site plan generally indicates the connection to the public network, but not always the details of the internal routing within the plot.
- The technical file provided by the builder or architect upon project completion. This document sometimes contains a plan of the buried networks, especially if the house was built after the 1990s.
- The sanitation compliance file, established after an inspection by the SPANC (Public Service of Non-Collective Sanitation) for individual installations, or after a connection to the public sewer system. This file may be more reliable than an initial plan if work has modified the installation in the meantime.
- Invoices and estimates from previous plumbing work, which sometimes mention the location of interventions.
An old plan or a site plan does not guarantee that the routing is still accurate. Work done after construction (adding a bathroom, moving an inspection chamber, connecting a rainwater collector) may have altered the path of the pipes without the plan being updated.
Ground detection: ground-penetrating radar and inspection camera when plans are missing
When no usable document exists, we move to on-site surveying. Two techniques dominate depending on the type of network being searched.
Inspection camera for water networks
A camera is inserted into an existing inspection chamber or access point. It progresses through the pipe and transmits in real-time the path, bends, connections, and the internal condition of the pipes. This method allows for mapping a wastewater or rainwater network with high precision, including sections buried under a slab or pavement.
The camera often carries a locatable transmitter from the surface, allowing the routing to be plotted on a plan. This is the most reliable solution for pipes accessible through an entry point.
Ground-penetrating radar and electromagnetic detection
For metallic pipelines (gas, drinking water in cast iron or steel), electromagnetic detection works well. Ground-penetrating radar complements this approach by also locating non-metallic pipes (PVC, clay, concrete) using radar waves that identify density variations in the soil.
The cost varies depending on the area to be covered and the complexity of the terrain. However, a professional survey produces a georeferenced plan that can be reused for all future work on the plot. For old houses with no archives, this is often the only way to obtain a reliable plan.
Rainwater recovery and separate circuits: a layout to document
Rainwater recovery installations add a layer of complexity. Non-potable water pipes must be clearly distinguished from the drinking water network, and their routing documented. In case of sale, the absence of this documentation can pose problems during the sanitation diagnosis.
Whether you have just purchased a house equipped with such a system or are planning to install a recovery system, mapping these circuits on an updated plan avoids confusion between networks and simplifies any future intervention. A complete plan, even if created by yourself after a site survey, remains a reference document for the lifespan of the building.
