LEAKS have been found in water supplies servicing one in 20 homes that have been fitted with meters over the past two months.
Repairs have been carried out in 600 of the 12,000 homes metered since last August, and the State now faces the prospect of being forced to undertake repairs in thousands of homes across the country.
Irish Water confirmed that local authorities had carried out repairs after leaks were detected in mains pipes outside properties during the installation of meters.
In six weeks' time, Irish Water staff will begin monitoring water usage to determine if separate leaks are in pipes running into the house – which the Government has promised to fix for free.
If the 5pc leakage rate is replicated across the country, up to 50,000 homes could be affected.
Experts put the cost of fixing a leak at up to €600 each – meaning the final bill could be more than €30m.
"Where we open a hole in the pavement to put in a boundary box (which holds the meter), and we detect a leak, we notify the local authority which repairs it," a spokesman said.
"We don't believe at this stage that the 5pc is the average as they have yet to go out across the country. When we have an area completed, in four to six weeks, we will read meters by driving by and see if there's constant flows. If there's a constant flow, it tells you there could be a leak."
Some 12,000 meters have already been installed in Fingal, Kildare, Kerry, Meath, Wexford, Limerick, Mayo and Dublin City. The metering programme will be rolled-out in all regions by year end, with 1.05 million to be installed by December 2016.
The extent of the leakage rates has previously been flagged in studies conducted by Galway City Council and Dublin City Council, with up to 6pc of all homes in the capital suspected of having a problem.
In many cases, homeowners will not be aware they have leaks as the water can be found under front gardens and may never appear on the surface.
Most leaks are found around the stopcock of fittings, but they could also be in the pipe which would require the pavement or garden to be dug up and the pipe replaced.
Detecting a leak on the pipe into the home involves using sounding equipment which is used to listen for a flow of water from a pipe under the ground. In the case of smaller leaks, tracer gas is used.
"It's very small minute percentage of hydrogen gas introduced into the pipe – the molecules are so small in hydrogen they leak out through the pipe, and comes to the surface where it's detected with a hydrogen detector," Alan Treacy from Smart Energy Systems based in Ennis, Co Clare, said.
A number of companies contacted by the Irish Independent said the likely cost of repairing a leak could run from €600 to €800, assuming it only took a number of hours to find. Older houses, serviced by metal pipes, were more likely to leak.
Average water use per person is estimated at 150 litres a day, but leaks can result in thousands of litres being wasted. A study by Galway City Council found that one home in the city was using 61,000 litres.
Water charges will be introduced from October next year, with the first bills to be issued the following January. Bills are expected to be around €350 per year.