A new report by the Environmental Protection Agency highlights 38 towns and villages in the country.
Over 30 towns and villages are still releasing raw sewage into the environment every day because they don't have treatment plants.
Three towns and villages in the midlands, Portarlington, Kilcormac and Ballymore, have been identified by the Environmental Protection Agency as areas where waste water is not properly treated.
Ballyroan in Laois is also on the list of towns and villages where treatment must improve to help protect freshwater pearl mussels.
The study also found that water collecting systems in Athlone must be upgraded and brought up to standard.
It shows 12 large towns and cities did not meet wastewater treatment standards that have been set to protect the environment.
These areas generate half of Ireland's wastewater.
Noel Byrne, from the EPA, says Irish Water needs to take more action to fix the problem:
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