Individual Water Meters: Metering in a Condominium

Individual sub-meters are secondary meters installed downstream of the condominium's main meter, one for each unit. They measure each apartment's actual water consumption, so the water bill can be split not only by thousandths (millesimi) but by the liters actually drawn. The consumption share follows the individual readings, while the fixed share of the service, independent of usage, remains split by thousandths. It is the fairest method because it ties the cost to each person's behavior.

Why install individual meters

Without sub-meters, water is split among owners by ownership thousandths, a criterion that ignores real consumption: a large family and a single person would pay in proportion to property value, not to liters used. Metering with individual meters corrects this distortion. Regulation of the water service has pushed toward installing individual meters in buildings, both new and, where technically possible, existing ones, to encourage saving and consumption-based allocation.

How the water cost is composed

The water bill is not made only of cubic meters consumed. It includes a variable share, proportional to consumption, and a fixed share that covers service costs, independent of usage. With individual meters the variable part is attributed to each unit based on the volumes recorded by its own meter; the fixed share, not tied to consumption, is usually split by thousandths under Article 1123, first paragraph, of the Italian Civil Code, or by the criterion set in the regulation or a resolution.

The offset and common consumption

The sum of the readings from the individual meters almost never matches the total of the main meter. The difference, called the offset or common consumption, includes garden watering, cleaning of common spaces, any network losses and the measurement tolerances of the meters. This residual share is split among everyone, usually by thousandths. Ignoring the offset means leaving a real part of the bill uncovered, which then emerges as a management deficit.

An owners' meeting resolution is needed

Moving from allocation by thousandths to consumption-based metering changes the allocation criterion of an expense, so it requires an owners' meeting resolution with the required majority, unless the contractual regulation already imposes it. The resolution sets the method, the frequency of readings, and the treatment of the fixed share and the offset. A criterion adopted without the required consent is exposed to challenge, because it affects how each person contributes.

Readings, adjustments and advances

• Periodic reading of the individual meters, with date and value for each unit.
• Attribution of the variable share based on each meter's consumption.
• Allocation of the fixed share and offset by thousandths or the resolved criterion.
• Advances during the year and final adjustment against those advances.
• Handling of faulty or unreadable meters with a justified estimate, to be regularized.

Faulty meter or missing reading

When an individual meter is faulty or inaccessible, the reading is missing and that unit's consumption must be estimated, for example on the apartment's historical average or on similar units' consumption, pending repair. The estimate must be justified and transparent, to avoid disputes. Maintenance and replacement of individual meters, if commonly owned or installed by the condominium, are expenses to be split according to their nature; if the meter is the individual's property, its replacement stays with the unit.

Handling metering without errors

Consumption-based metering demands rigor: recording readings, separating variable and fixed shares, calculating the offset and adjusting at year-end without missing a cubic meter. Management software keeps the reading history, applies the correct criteria to each item and produces a clear report for the owners' meeting. With AmministraPro you set water allocation by consumption with a fixed share by thousandths and handle advances and adjustments automatically: the features are described on the /funzioni page and the plans on the /prezzi page.