Short answer: tap water in Korea's cities is treated to a genuinely high standard and is safe to drink. Most Koreans still choose not to drink it straight from the tap anyway — that's more a matter of habit than safety.
The standard
Seoul's tap water, branded Arisu, is tested against far more substances than WHO guidelines require and is published openly by the city government. Other major cities run similar treatment standards. If you're in a hotel, café, restaurant, airport, or a reasonably new apartment, the water from the tap is fine to drink.
The caveat
Water quality can drop between the treatment plant and your glass — older buildings with ageing indoor pipes or poorly maintained rooftop tanks are the actual risk, not the city supply itself. If the water looks cloudy or rusty, smells off, or you're somewhere you have no read on, switch to bottled or filtered water for that stop.
In practice
- Restaurants routinely put out a jug or dispenser of water at the table — this is standard tap water and normal to drink.
- Bottled water is cheap and everywhere (corner stores, vending machines) if you'd rather not think about it at all.
- Filtered water coolers are common in guesthouses, hostels, and offices — always safe to use.
Last updated