Water losses in São Paulo – the effect of the water meters´  errors on the billing.


The São Paulo Metropolitan Area (SPMA) has about 2.5 million water house connections. The houses in the SPMA are 100% metered, and, probably 100% equipped with at least one water storage tank.


The water tank, upstream of the meter, is installed on the roof of the house from which the usual points of consumption are supplied (faucets, flush valve, shower etc.  ...). Whenever there is water consumption at one of these points, the storage tank is refilled.


We performed an experimental investigation and we verified that the refilling of the storage tanks induces low flows which are not registered by the water meters. At that time, 2006, this hypothesis was considered quite likely among technicians from the utility company and manufacturers, but it had not been yet checked in a systematic way.


We concluded that the water meters do not register 16% of the consumed water in SPMA. From this 16% index the water utility company concluded that the non-physical loss in State of São Paulo was 196 million gallons/day which represents a non-revenue value of  $0.69 billion a year for the company.