Irish Water is under pressure to clarify the extent and spread of water lost from the system as the country enters day two of a six-week hosepipe ban.
The Water Advisory Body (WAB), set up to oversee the utility, has reported difficulty separating the volume lost through leaks from other unaccounted for water.
It pointed out unaccounted-for water can also include unbilled water, such as that used by fire services and Irish Water itself, as well as water lost through unauthorised or faulty connections.
The WAB highlighted that regularly cited leakage data does not include leaks on individual properties.
Those leaks are reported separately as part of Irish Water's 'first fix' scheme, but the last publicly available data on that is from March 2019.
"The body is of the view that it is only through accessible and easily understood data that we can hold Irish Water to account for its performance in tackling leakage and water losses," chairman Paul McGowan said.
Irish Water cites a leakage rate of 42.3pc nationally, meaning more than 700 million litres are lost daily through leaks before reaching the taps. The figure for the Greater Dublin Area is slightly smaller, at 37.5pc. Irish Water said the rate nationally was 49pc when it took over control of the water network in 2014.
But it is not yet clear how much is due to what the industry terms 'real water losses' and how much to other issues.
Irish Water finished rolling out a new high-tech leakage management system countrywide at the end of 2019.
"The first report of real water losses is expected to be available in the next few weeks," said Mr McGowan.
"The Water Advisory Body welcomes this development as it will ensure that all stakeholders will have clear visibility of Irish Water's performance in this key area."
But Irish Water insisted its figures were already robust.
"Leakage calculation is a challenge for every utility when trying to account for unmetered losses, operational usage, unrecorded connections, etc," it said.
"As our network is 63,000km long and has 12.5 million joints, it is not possible to be 100pc accurate, but we are confident that the leakage statistics we report on are as robust as we can achieve at this time.
"We are continually refining our calculations based on our own experience and by referencing international benchmarks and best practices."
Irish Water also said it was on track to reduce leakage to 38pc nationally by 2021.
But the WAB said it was concerned that the rate of leak repairs had fallen since 2016.
Aontú leader Peadar Tóibín said the situation was evidence of a "crisis" in the water system.
"The Government needs to get real. The annual 'stop watering your flowers' announcement that comes every time we experience even the mildest of heatwaves just highlights our ever creaking system," he said.
Irish Water reported no change yesterday in the drought conditions that led to the imposition of a nationwide water conservation order from midnight on Monday.
Some rain fell yesterday, mainly in the east of the country, but only scattered showers are forecast for the remainder of the week.