Common Drainage Stacks: Who Pays and Who Is Liable

The vertical drainage stacks that cross the building to collect wastewater from the various apartments are common parts of the condominium under Article 1117 of the Italian Civil Code, since they serve several units. The horizontal branch that splits off from the stack to serve a single apartment, on the other hand, is the exclusive property of the owner who uses it. Everything depends on this distinction: who pays for maintenance, who is liable for leaks and how costs are shared when the pipe breaks or clogs.

The Article 1117 rule

Article 1117 includes among the common parts the works, installations and structures intended for common use, such as pipework and systems up to the branching point towards individual properties. The rising stack, which receives the discharge from all floors and channels it towards the sewer network, has an objectively common function and is therefore a condominium asset, unless a title provides otherwise. Its preservation is a burden falling on the whole condominium community.

Where the common ends and the private begins

The boundary between common and private part lies at the branching point: from there on the pipe serves a single apartment and belongs to that owner. The common vertical section remains a condominium asset, while the horizontal stretch entering the unit is private. This dividing line is decisive for attributing cost and liability, because it identifies who must act and to whom the work must be charged.

• Vertical rising stack serving several floors: common part, cost borne by all owners through thousandths (millesimi).
• Horizontal branch serving a single apartment: exclusive property, cost borne by the owner.
• Branching point: threshold separating common from private liability.
• Contrary title: only a deed or a contractual regulation can change this attribution.

Maintenance costs of the common stack

Cleaning, unclogging, repairing and replacing the common drainage stack are condominium costs and are shared among all owners in proportion to the thousandths of ownership, under Article 1123 of the Italian Civil Code. If the stack serves only part of the building, for example a single staircase or a single block, the cost falls only on the owners of that portion, following the logic of the partial condominium. The manager must check which units are actually served by the stack before setting the allocation.

Who is liable for leaks

When a leak damages an apartment, liability follows the ownership of the pipe that failed. If the common stack is what breaks, the condominium is liable as custodian of the common asset, under Article 2051 of the Italian Civil Code on liability for objects in custody. If instead the leak comes from an owner's private branch, that individual owner is liable. Before approving or rejecting a compensation claim, the manager must have the stretch of pipe at the origin of the leak established, usually with a technical check or a video inspection.

Blockages and improper use

A frequent case is the clogging of the common stack caused by improper use, for example the introduction of prohibited materials by an owner. In that case, if it is proven that the blockage is attributable to specific conduct, the unclogging cost can be charged to the responsible party and not shared among all. If instead the blockage results from normal ageing or physiological scaling, the cost is common. The distinction between objective wear and negligent conduct, as for slabs, always guides the allocation.

Extraordinary works and meeting resolution

The full replacement of a deteriorated drainage stack is extraordinary maintenance that must be approved by the owners' meeting with the majorities of Article 1136 and, if of significant amount, accompanied by the special fund provided by Article 1135. It is good practice to attach to the estimate a report identifying the common stretch to be rebuilt, so as to clearly separate it from any private branches that remain the responsibility of individual owners. This transparency reduces disputes over the allocation.

Distinguishing common and private stretches, managing thousandths and partial allocations and archiving technical checks is easier with orderly management software. With AmministraPro you can set allocation criteria for groups of units, keep video inspections and minutes and track liability for each system: the features are described on the /funzioni page and the plans on the /prezzi page.