Irish Water has said it could take six years before boil water notices are eliminated.
It has published an investment plan today, outlining its priorities for the next 25 years.
The company says it could take 10 years to remove all lead piping from the public mains and sets a 25-year time frame before the water system is at an acceptable level.
A lack of funding also means the company has to reduce investment in the network by €300m between now and the end of next year.
Head of asset management with Irish Water Jerry Grant said it would be difficult to remove all leaks, as even countries with state-of-the-art systems have issues.
"The very best are losing between 6% to 10% (to leaks)," he said. "In the Netherlands, they have a completely new plastic pipe syem and tend to have much more convenient ground conditions...and they're down to 4% to 5%.
"Across northern Europe (the figure) is around 10% to 12% and Britain is between 20% and 25%."