More than €12 million in revenue slipped through the hands of the Water Services Corporation last year because of unbilled water consumption.
The figure is equivalent to more than half the subsidy received from the government.
Unbilled water consumption is a result of the under-registration of meters, inaccuracies and theft, according to the WSC's annual report. In contrast, the revenue generated from fines was €25,000.
In its report, the WSC said the total production of water in 2008 was 30.8 million cubic metres. A spokesman told The Sunday Times that apparent losses (water consumed but not billed) last year stood at 23 per cent.
If sold at the average billing price in 2008 of €1.73 per cubic metre, the income would have been €12.3 million.
The corporation closed 2008 with a loss of €697,372 after taking into consideration government subsidies amounting to €21.7 million.
Domestic water meters and theft have a major impact on apparent losses. In its annual report, the corporation admits that "although it is not a loss of water, it is a considerable loss of revenue."
On top of the loss of revenue resulting from unbilled water consumption, another 450 cubic metres per hour of water are lost due to leakages during distribution.
While the wastage seems high, it is 200 cubic metres per hour less than the same month of the preceding year.
WSC CEO Marc Muscat said that the water operations section, through continuous leakage detection and rectification, reduced potable water production by a further 0.4 per cent over the previous year.
The reduction was the result of the decrease in water wasted during distribution, which appears to have been the focus of the corporation in recent years. The report emphasises reductions in real losses (leakages) but makes no mention of any reduction in apparent losses, which is the result of inefficiencies.
He said the corporation would be focusing on apparent losses by continuing research in this area together with in-depth studies on intelligent metering in order to tackle revenue-loss issues.
A major study investigated the cause and magnitude of under-registration of domestic water meters which has a big impact on apparent losses.
Findings concluded that the widespread use of roof storage tanks which supply households with most of the water consumed involves an indirect plumbing set-up that has a great bearing on meter performance.
In tandem with the project on meter under-registration conducted in Malta, a pilot project was launched in Gozo whereby residents' water meters were replaced in Zebbug.
Readings taken following the replacement of meters showed a reduction of 10 per cent in apparent losses in the area.
Meanwhile, the price of water has risen steadily. According to figures quoted in Parliament, there has been a 123 per cent increase in the average price per cubic metre of water over four years.
In 2006, 17.8 million cubic metres of water had been billed at an average €1.42 per cubic metre, rising to an average billing price of €3.23 for 17.5 million cubic metres in 2009.