Irish Water has said more than €2 billion will need to be invested on water and wastewater projects over the next four years.
Under its latest plan - 'A Summary of Irish Waters Infrastructure Investment Need' which was seen by RTÉ's Morning Ireland - the utility says that almost €2.1bn will need to be spent between 2017 and 2021 on schemes to improve water quality, securing supply and reducing water leakage.
The figures follow two major disruptions of water supply in the northeast in recent weeks.
The utility reports that it spent €860 million on water and wastewater projects between 2014 and 2016.
Under the plan, a number of counties would see massive increases in investment to upgrade their water and wastewater systems.
Irish Water said that government funding for water and wastewater projects is committed for this year and next year.
The utility said "after that it is a matter for government".
The plan states that Dublin, Donegal, Sligo, Cork, Westmeath, Meath and Louth would get boosts to funding of tens of millions of euro.
It plans to spend €827 million in Dublin on improving water and wastewater services over the next four years, an increase of €648 million compared with what was spent between 2014 and 2016.
In Donegal, €151m would be invested, which is almost six times what was spent between 2014 and 2016, while Louth would see an increase from €7m up to €40m between 2017 and 2021 under the plan.
Six counties would receive less funding than before.
Carlow would see funding reduced from €19m to €12m while Offaly's investment would be cut by €6m.
Investment in Limerick would see a cut of 64% to €10m under the plan.
Irish Water plans to spend €2bn+ over next 4yrs to upgrade services. Where will it go? Here are details as heard on @morningireland @rtenews pic.twitter.com/kOf294Qizf
— Jackie Fox (@jackiefox_) August 2, 2017
Sinn Féin's Housing spokesperson Eoin Ó Broin said Irish Water's spending plan was not enough.
Mr Ó Broin, who is also a member of the Oireachtas Water Charges Committee, said there is a need for increased investment in water infrastructure and an urgent repair of certain water plants.
He said local authority water service engineers and the Environmental Protection Agency had highlighted many areas where improved infrastructure was needed.
"I have been speaking to local engineers who are putting in applications for projects and getting refused," he said.
He said more investment could be funded by extra borrowing, income from commercial water users and direct government investment.
"Sinn Féin outlined how that can be achieved last year. We identified an additional €340 million which we felt was necessary."
