Splitting metered water costs in an Italian condominium

Splitting metered water costs in an Italian condominium is one of the topics that sparks the most debate at the owners' meeting, because it directly affects how much each household pays every year. When the building has individual meters, the logic changes compared with the old thousandth (millesimal) split: instead of dividing by the value of the property, the cost follows the cubic metres actually drawn by each unit. The outcome is fairer, but it needs a clear method and carefully recorded figures.

Why the move to actual consumption

Splitting water only by millesimal tables means charging an apartment for its floor area, not for what it uses. Two identical units can have very different consumption: a couple who work away all day draw far less water than a large family. Individual meters exist precisely to capture the real draw of each unit and to distribute the water bill in proportion to use.

The mixed system: fixed share and variable share

With individual meters a mixed system is normally adopted, made up of two parts. The fixed share covers common consumption and costs that do not depend on private use; the variable share is the larger part and follows the cubic metres recorded by each meter. The ratio between the two shares should be set in the building rules or by a meeting resolution, so that everyone knows in advance how the bill will be divided.

What the fixed share covers

The fixed share includes the items that serve the whole building: water used to wash the stairs, water the garden, run the common areas, plus small physiological network losses and the cost of managing the service. This part is usually split by the millesimal tables of ownership, because it relates to a common asset rather than individual use.

What the variable share covers

The variable share is the part tied to real consumption. Each apartment pays in proportion to the cubic metres read on its meter for the period. This is the component that makes the split fair, because it links the cost directly to each occupant's behaviour.

The cost per cubic metre is not driven by the drinking-water rate alone: the bill also includes the sewerage and treatment components, on top of the utility's fixed charges. Applying the same unit rate to all metered cubic metres, including the sewerage and treatment components that follow consumption, ensures everyone pays consistently with what they actually drew.

General meter versus the sum of sub-meters

An important technical point is that the sum of the readings on the individual meters almost never matches the consumption recorded by the building's general meter, the one the utility bills against. The difference comes from network losses, common consumption that is not metered and measurement tolerances. This gap has to be allocated and cannot be ignored, otherwise the figures will not reconcile.

What to do when individual meters are missing

If the condominium has no individual meters, or only some, the consumption criterion cannot be used for everyone. Without suitable meters the prevailing view is to split the entire water cost by the millesimal tables, because that is the only objective parameter available. Installing sub-meters is therefore the first step toward a metered split, and the decision must be taken at the meeting.

How to set up a correct split

• Set the ratio between fixed and variable share in the building rules or a resolution.
• Collect the readings of all individual meters for the same period.
• Allocate the variable share by the cubic metres read for each unit.
• Allocate the fixed share and the general meter gap by the millesimal tables.
• Attach the readings and the utility bill to the statement for verification.

A metered split is fair only if the readings are complete and taken for the same period: a missing reading shifts that unit's consumption onto the others.

The most frequent mistakes

The most common errors are collecting readings on different dates, forgetting to allocate the gap between the general meter and the sub-meters, and not updating the millesimal tables used for the fixed share. A poorly documented split is easily challenged at the meeting and slows the approval of the statement, besides complicating the recovery of sums owed by those who do not pay.

Metered water splitting with management software

With management software, splitting metered water becomes a repeatable operation: you enter the meter readings, set the fixed and variable rule once, and the program calculates each unit's share, automatically distributing the general meter gap. The readings stay attached to the statement, so every owner can verify how their amount was reached.

AmministraPro handles metered water splitting with a fixed share by millesimal tables and a variable share by meter, attaching readings and supporting documents to the statement. You can see how it works on the features page or compare the plans in the pricing section.