The boil water notice issued on Tuesday remains in place for large areas of counties Dublin, Kildare, and Meath.
Hundreds of thousands of people saw their water supply disrupted after testing revealed the presence of pathogens.
Areas affected include Artane, Ashtown, Balbriggan, Baldoyle, Ballyboghill, Celbridge, Clonee, Clonsilla, Coolock, Coolquoy, Corduff, Darndale, Donabate, Dunboyne, Finglas, Garristown, Glasnevin, Howth, Kilbarrack, Kilclone, Killester, Kinsaley, Leixlip, Lusk, Malahide, Maynooth, Naul, Palmerstown, Poppintree, Ronanstown, Rush, Skerries, St Margaret’s, Straffan, Sutton, and Swords.
Irish Water has admitted that it cannot confirm when the notice will be lifted as contaminated water remains in the piping system.