Is Tap Water Safe to Drink in Koh Samui?
No, tap water on Koh Samui is not safe to drink. The island’s water supply is managed partly by the Provincial Waterworks Authority and partly by private operators, with inconsistent treatment and distribution quality.
Water Source
Koh Samui relies on a mix of surface reservoirs (Hin Lat, Tha Nee), groundwater borewells, and small private desalination plants. The island’s rapid tourism development has outpaced water infrastructure capacity.
Contaminants & Concerns
Inconsistent treatment quality, saltwater intrusion into coastal wells, and unregulated private suppliers create an unreliable mix. Bacterial contamination from ageing pipes and overloaded sewage systems is common, particularly during the rainy season. Some private borewell-supplied accommodations have elevated mineral content.
Tips
- •Drink bottled water exclusively — the cheap 1.5L bottles sold at 7-Eleven and Family Mart are safe
- •Most resort restaurants use purified water for cooking and ice, but confirm at budget establishments
- •If renting a long-term villa, install a countertop RO filter for drinking and cooking water
Frequently Asked Questions
Sources & References
The safety rating and guidance on this page draw on the following sources. See our full methodology.
- •WHO Guidelines for Drinking-water Quality
- •CDC Travelers' Health destination pages
- •The municipal water utility's published quality data