A no-bathing notice has been issued for Kilkee beach, Co Clare, after a discharge of wastewater into the sea.
Irish Water said the incident was as a result of a burst pipe following heavy rain.
Clare County Council said red flags are in place at Kilkee beach and the blue flag has been removed until water quality tests allow for a lifting of the notice.
"On the advice of the HSE and in the interest of public health, members of the public are advised not to swim or engage in other recreational activities in the water at this time," the council said.
In a statement, Irish Water said it regretted the impact of the burst pipe.
It said a storm rising main had burst causing the discharge of sewage to a watercourse which flows onto the beach.
Irish Water said the no-bathing notice would remain in place, "pending sampling results of the bathing waters by Clare Council.
"It is hoped at this point that Clare Council in consultation with the HSE can remove the notice by early next week."
Dún Laoghaire-Rathdown County Council has imposed restrictions at Seapoint, Sandycove, the Forty Foot, Killiney and White Rock until at least 3pm on Monday, "pending water quality test results following wastewater overflow from Irish Water treatment plants".
Dublin City Council has also placed no-bathing notices at Dollymount, Merrion and Sandymount beaches after what it said was a significant overflow from the storm storage plants at the Ringsend Wastewater treatment plant into the River Liffey.
Bathing prohibitions were already in place for the entire 2019 bathing season at Sandymount and Merrion beaches due to general water quality.
Irish Water said the stormwater overflows in Dublin, "operated in compliance with regulations, and was fully screened and settled".
It said the no-bathing advice remains in place pending further sampling results of the bathing waters next week.
"It is hoped at this point that the notices can be lifted. Notices are displayed at the beaches and on the Environmental Protection Agency website advising the public of the restrictions."
