A boil water notice affecting over 600-thousand people may be in place for a number of days.
Irish Water has warned that the supply may be contaminated in areas within parts of Fingal, Dublin City Council, South Dublin County Council, Kildare and Dunboyne in Meath.
It's as a result of a mechanical fault at a water treatment plant in Leixlip, which has since been repaired.
Yvonne Harris from Irish Water says the untreated water that got into the system could pose a health risk: 'There's a risk that there could be bugs in the water, Cryptosporidium is one that people would be familiar with. We hope that this will not impact our customers but if anyone is feeling unwell or is concerned they should visit their GP'.
As a result of the boil notice, bottled water is in high demand in supermarkets and shops in the Dublin area.
People have completely wiped Tesco in Blanchardstown clean of its water. They'd rather die of thirst than drink sparkling! pic.twitter.com/ykbb737MuC
— Ian Begley (@IanBegley_) October 22, 2019
— Ed King (@edking28) October 22, 2019