It would see water pumped from the River Shannon to Dublin.
A controversial pipeline from the River Shannon to Dublin remains the only viable option to keep up with demand.
Irish Water has examined almost 600 potential sources but says the plan remains the best solution for the capital and parts of the east and midlands.
A public consultation on improving supply for the regions began today.
Lawyer Emma Kennedy of Kennedy Analysis says the €1.3 billion price tag would be better spent fixing leaks:
Angela Ryan from Irish Water says they looked at dozens of options including pumping 300 million litres of water a day from the Shannon.
She says the pipeline is part of their preferred approach:
The utility says the pipelone project, along with upgrades to treatment plants and the addition of new facilities, will help improve water supplies for the east and midlands.
There are also plans to reduce water loss through leaks by around half by 2033.
But Ms. Kennedy says the pipeline isn't needed:
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