Six Clare towns and villages are among 45 areas around the country where raw sewerage is being discharged.
A new report from the Environmental Protection Agency shows that Kilkee, Kilrush, Ballyvaughan, Clarecastle and Liscannor are among the areas where waste water received no treatment prior to discharge.
Shannon is also listed as on of 31 large urban areas which are non-compliant.
The EPA says failure to properly treat sewage "can pose a risk to human health and the aquatic environment".
But in a statement, Irish water says the discharge of untreated sewage at 45 urban locations will end by 2021.
The company says it plans to invest another 2 billion euro in wastewater infrastructure over the next six years.