Northern Ireland's leaky water system is losing around 157 million litres a day, it was revealed today.
The cost to the taxpayer was around £5 million last year, Regional Development Minister Conor Murphy said.
Inadequate infrastructure investment over many years and faults with private supplies and service reservoirs were to blame.
Northern Ireland Water (NIW) has undertaken a major plan to detect faulty connections.
DUP Assembly member Alastair Ross said: "This will be very alarming to those people who are already paying for their water, and many householders who face the prospect of paying for their water in future years.
"It is clear that if we are indeed to pay for our water then consumers should not be asked to foot the bill for leaky pipes."
NIW welcomed his recognition of its work to reduce leakage.
"NI Water proactively monitors the distribution system on a daily basis and implements action where abnormal flows are detected," a spokeswoman said.
"We take the issue of leakage extremely seriously and are working hard to build on the progress we have made over recent years."