A Do Not Consume water notice on Whiddy Island in Bantry Bay is to remain in place until further notice, according to Irish Water.
The island is home to 22 permanent residents and the Whiddy Island oil terminal.
The warning was first issued last September when the quality of the drinking water on the island was affected by low water levels at the raw water extraction point.
Improvement works have been carried out by Irish Water working with Cork County Council and the final commissioning is ongoing, according to Irish Water's, Neil Smith.
Mr Smith said water quality sampling is due to get under way shortly to see if the notice can be lifted or if further remediation works will be needed.
"Public health remains our number one priority. We would like to thank the people of Whiddy Island for their patience and cooperation throughout this Do Not Consume Notice, especially as it was ongoing over the Christmas season. I would like to remind everyone that bottle water remains available at 'The Bankhouse' on the island."
