Irish Water says it's working with the County Council to resolve the issue as soon as possible.
A boil water notice has been put in place for 1,500 people in Co Westmeath.
It affects those served by the Castlepollard high level public water supply, and will remain in place until further notice.
Areas affected are Ballymanus, Hilltown, Slieveboy, Loughpark, Fore, Martinstown, Glenidan, Cummerstown, Collinstown, Ranahan and surrounding areas.
Irish Water says, after consultation with the HSE, the decision was made as a precaution, following mechanical issues with the disinfection process at the treatment plant.
It says it's working with Westmeath County Council to resolve the issue as soon as possible.
Irish Water says it acknowledges the impact and inconvenience caused by the imposition of a boil water notice, and wishes to thank the community for their patience and cooperation.
The company also says it's contacting registered vulnerable customers who are affected by this notice to advise them.
Should customers have any queries, they should contact Irish Water directly on the customer care helpline.
Updates are available on the Water Supply Updates section on their website, on Twitter @IWCare, and via the customer care helpline, open 24/7, on 1850 278 278.
Advice from Irish Water:
Water must be boiled for:
• Drinks made with water
• Preparation of salads and similar foods, which are not cooked prior to eating
• Brushing of teeth
• Making of ice - discard ice cubes in fridges and freezers and filtered water in fridges. Make ice from cooled boiled water.
What actions should be taken:
• Use water prepared for drinking when preparing foods that will not be cooked (e.g. washing salads)
• Water can be used for personal hygiene, bathing and flushing of toilets but not for brushing teeth or gargling
• Boil water by bringing to a vigorous, rolling boil (e.g. with an automatic kettle) and allow to cool. Cover and store in a refrigerator or cold place. Water from the hot tap is not safe to drink. Domestic water filters will not render water safe to drink
• Caution should be taken when bathing children to ensure that they do not swallow the bathing water
• Prepare infant feeds with water that has been brought to the boil once and cooled. Do not use water that has been re-boiled several times. If bottled water is used for the preparation of infant feeds it should be boiled once and cooled. Bottled water can also be used to make up infant formula. All bottled water, with the exception of natural mineral water, is regulated to the same standard as drinking water. It is best not to use bottled water labelled as ‘Natural Mineral Water’ as it can have high levels of sodium (salt) and other minerals, although it rarely does. ‘Natural Mineral Water’ can be used if no other water is available, for as short a time as possible, as it is important to keep babies hydrated.
Great care should be taken with boiled water to avoid burns and scalds as accidents can easily happen, especially with children.