Heavy rainfall in the Slieve Bloom Mountains is the cause.
A boil water notice has been in effect for parts of midlands for two weeks.
The warning was first issued by Uisce Éireann on the 20th of June, with households in Tullamore South and Clonaslee affected.
It's since been lifted in Colliers Brook Estate and Spollanstown Industrial Estate, but remains in place elsewhere.
The issue was caused by heavy rainfall in the Slieve Bloom Mountains.
Customers are being advised to boil and cool their water before use.
Read More: Heavy Rainfall To Blame For Midlands Boil Water Notice
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