Why the city says Arisu is drinkable
Arisu is the name of Seoul’s municipal tap water. Seoul Water says advanced treatment has supplied the whole city since 2015 and that the system received ISO 22000 food-safety management certification in 2016. Its current English introduction says quality is managed across 362 parameters.
A 2026 Seoul Metropolitan Government notice also describes a free household water-quality verification program. Specialists can test five indicators at a faucet and recommend follow-up action. That matters because a treatment plant result and water coming from one building’s tap are related, but they are not exactly the same measurement.
What about an older hotel or apartment?
The municipal supply can meet drinking-water standards while a building has its own tank, internal pipework, faucet filter or maintenance issue. Visitors usually cannot inspect those systems. Ask the front desk whether the cold-water tap is intended for drinking and whether there has been recent plumbing work, a water shutdown or a building notice.
Use the cold-water tap for drinking and cooking unless the property gives different instructions. Hot water may pass through a separate heater or tank. If a room has a dedicated filtered-water dispenser, follow its maintenance instructions rather than assuming it is automatically better.
Should you let the tap run first?
Seoul Water’s Korean guidance recommends letting stagnant water run, particularly at the first use of the day or after the property has been empty for several days. The site suggests roughly two to three minutes in those circumstances and reusing that water for washing rather than wasting it. In an occupied hotel room, a shorter flush until the water runs cold may be enough, but follow the property’s advice.
Does chlorine taste mean the water is unsafe?
A mild disinfectant taste can occur in treated water and is not, by itself, proof of contamination. Chilling water in a clean glass container can improve taste. A strong new odor, however, deserves a check with the property. Do not add an unmaintained travel filter and assume it solves every possible problem; filters require correct cartridges and cleaning.
Can you refill a bottle?
Where a public drinking fountain or refill station is clearly marked and operating, use it as instructed. At a café or restaurant, ask rather than filling from a staff sink. Carrying a reusable bottle can reduce single-use plastic, but wash it daily and avoid touching its mouth to a public dispenser.
Decision checklist for visitors
- Confirm you are in Seoul; this article does not certify every private water system in Korea.
- Ask the accommodation whether the cold tap is intended for drinking.
- Flush stagnant water after a long period without use.
- Use only clear water without an unusual odor or active warning.
- Keep the bottle or container clean.
- If uncertain, use sealed water temporarily and ask the property or Seoul’s 120 Dasan Call Center.