More than half of all the water taken from reservoirs, rivers and wells leaks away before use, according to documents supplied by Irish Water to the Oireachtas water committee.

In all Irish Water supplies 1.7 billion litres daily. Of that 765 million litres leaks because of faults in an ageing public water system, while 170 million more litres leaks away because of faults in households.

Meanwhile, half of the district water meters installed by local authorities at a cost of €130 million had stopped working because they were not maintained after they were fitted, according to Irish Water.

The fault in the district meters installed between 2000 and 2010 was discovered in 2014, and have been fixed since Irish Water’s creation, the semi-State told the water charges inquiry.

Currently 4,407 district meters are in action: they can monitor the usage of between 50 and 100 homes in rural Ireland, and between 1,000 and 1,500 in towns and cities.

District metering will play a “crucial” role in dealing with decades-old problems in the system over the next 10 to 20 years, Irish Water’s Jerry Grant told TDs and Senators.

Irish Water has said that specially-equipped vehicles which will be able to read data from meters will be able to pinpoint leaks many times faster than existing methods.

District metering can help to narrow down where leaks happen but no more than that, says Martin Lane, managing director of Watersave Ireland. “We are talking about narrowing a leak down to a 5km radius or a 1km radius.”

Households

“For example, we now know that 1 per cent of households use over 20 per cent of all of the water supplied to households. We also know that 5 per cent of households use a third of the water supplied to households.

“Due to having a leak alarm on individual meters we also know that about 7 per cent of houses have continuous night flows that are very indicative of leaks.”

The Green Party criticised Fianna Fáil’s proposal to use the 2007 Water Services Act to prosecute wasteful households, insisting that house metering remained the fairest and simplest option.

Meanwhile, a think tank, PublicPolicy.ie, said it was “simply not credible” that 50,000 people could be taken to court and prosecuted for excessive use of water under the Water Services Act.

Ironically, the decade-old but never used legislation could see Irish Water itself prosecuted for waste as it struggles to upgrade a system that requires €13 billion to be spent on it in coming years.

Under section 56 of the Act which deals with water conservation, a person or corporate body may be prosecuted if a person “fails to prevent water from being wasted or consumed in excessive amounts”.

Offenders

Fines of up to €5,000 can be imposed, though section 14 (1) of the Act provides that where a “corporate body”, instead of a householder, is involved the penalties may apply to corporate directors, owners, managers or occupiers.

Neither the Environmental Protection Agency not the Department of Housing could provide instances of prosecutions of householders under the 2007 Water Services Act yesterday.

However, Fianna Fáil Laois-Offaly TD Barry Cowen, who has the party’s stand on water charges, said he could recall corporate prosecutions “from my days on the council”.

Under the Act, Irish Water, as the water services authority, can recover the costs against offenders if it has to repair connections that are so “defective, foul or neglected” as to to endanger human health.