Korean winters bring many days when temperatures drop below freezing. Frozen and burst water pipes or boiler lines — called pipe freeze accidents (동파) — can happen, and heating bills can spike. Knowing what to look out for and preparing ahead of time goes a long way toward preventing these problems. This guide covers what cold wave alerts mean, how to prevent frozen pipes, and how to save on heating costs. When a cold wave is forecast, it is also worth reading the companion guide on Winter Cold Wave Action Tips and Cold-Weather Illness Response.

What Is a Cold Wave Alert?

When a serious cold spell is expected, the Korea Meteorological Administration (KMA) issues a cold wave alert (한파 특보). There are two levels.

LevelConditions for Issue
Cold Wave Advisory (한파주의보)Morning low temperature is forecast to drop 10°C or more from the previous day to 3°C or below AND 3°C below the seasonal average OR morning low is forecast to stay at or below -12°C for two or more consecutive days
Cold Wave Warning (한파경보)Morning low temperature is forecast to drop 15°C or more from the previous day to 3°C or below AND 3°C below the seasonal average OR morning low is forecast to stay at or below -15°C for two or more consecutive days

You can check cold wave alerts and local weather information through the official KMA weather app or at KMA Weather Nuri (weather.go.kr). Detailed criteria for issuing weather alerts are on the KMA Special Weather Announcement Standards page. The Ministry of the Interior and Safety (MOIS) National Disaster Safety Portal (safekorea.go.kr) also provides public action guidelines for cold waves. Please verify the latest information with the Immigration Contact Center (1345) or your local Korea Immigration Service (KIS) office before taking any steps.

The recommended indoor temperature in winter is 18°C to 21°C. Setting it too high raises your heating bill; setting it too low is not good for your health.

What Is a Pipe Freeze Accident?

A pipe freeze accident (동파, 凍破) happens when water inside a water pipe or boiler line freezes, expands in volume, and bursts the pipe. Once this happens, repair requests flood in and you could be without water for several days. Prevention is by far the most important step.

Each year from November through March, the KMA publishes a Pipe Freeze Risk Index (동파가능지수) that shows the likelihood of pipes and meters freezing, in four levels (Low / Moderate / High / Very High), broken down by area and updated every three hours. You can check it through the KMA Weather Nuri Daily Life Weather Index page.

How to Prevent Pipe Freeze Accidents

For step-by-step action tips organized by temperature threshold (below -5°C, -10°C, and -15°C) that you can act on right away, see the companion guide Winter Water Pipe and Boiler Freeze Prevention Methods.

Boiler Care

  • Do not turn the boiler completely off when you go out. Instead, press the Away (외출) button. Turning the boiler off entirely can let the pipes freeze.
  • Wrap any boiler pipes that are exposed to the outside with old clothes, fabric scraps, or styrofoam, and seal any gaps with tape.
  • Wrapping a heating cable (열선 / heat tape) around water pipes or boiler lines is also effective. However, wrapping the cable too tightly or layering it under insulation material creates a fire risk, so take care.

If you are unsure how to use your boiler or find the Away mode, see the guide How to Use an Ondol Boiler: Operating Rinnai, Kyungdong Navien, and Other Models.

Water Meter Care

  • Seal any gaps inside the water meter box, and pack it full with insulating material such as old clothes, towels, or styrofoam.
  • Cover the lid as well and block it with plastic or similar material so cold air cannot get in.
  • If you will be away for an extended period, leaving a faucet open just enough to let a thin trickle of water flow continuously helps prevent freezing.

Washing Machine Care

  • Keep the washing machine covered with a blanket or duvet to maintain warmth.
  • Drain any remaining water from the washing machine’s drain hose in advance.
  • For drum-type washing machines, it is a good idea to disconnect the inlet hose from the faucet.

Window Insulation

Attaching bubble wrap (에어캡, commonly called 뽁뽁이 in Korea) to drafty windows reduces cold air coming in and improves heating efficiency. For how to do this, see the guide Winter Window Insulation: How to Apply Bubble Wrap (에어캡).

What to Do If a Pipe Freezes

Take a breath and work through these steps in order.

  1. Thaw the pipe slowly. Wrap it with a warm wet towel, or gradually apply warm water at around 50-60°C or use a hair dryer.
  2. Do not use boiling or very hot water. Pouring water that is too hot all at once can crack the meter or the pipe.
  3. If a pipe has already burst, immediately close the main shutoff valve (지수전) that controls water coming into your home, then report it using the contact numbers below.

Emergency Contact Numbers

AreaContact
All of SeoulDasan Call Center 120 (no area code needed) / Seoul Arisu Waterworks (arisu.seoul.go.kr)
All other areasYour local waterworks office or municipal services hotline
  • For waterworks office phone numbers outside Seoul, check the website of your local city, county, or district office (시·군·구청).
  • For weather-related questions or inquiries about the Pipe Freeze Risk Index, you can contact the KMA weather consultation line 131 (paid call).
  • Please verify all figures, deadlines, and responsible agency information with the Immigration Contact Center (1345) or your local Korea Immigration Service (KIS) office before taking action.

How to Save on Boiler Heating Costs

Choose the Heating Mode That Suits Your Home

Most boilers have two modes: room-temperature heating (실내난방) and ondol floor heating (온돌난방).

  • If you sleep in a bed and your home has little draft — room-temperature heating mode is usually more suitable.
  • If your room controller (remote panel) is near a window — ondol floor heating mode tends to be more efficient.

Save Through Daily Habits

  • Use hot water in one longer session rather than in many short bursts. The boiler uses extra energy each time it starts and stops, so running it less frequently is more efficient. (Hot water use actually consumes more gas than space heating.)
  • For outings of six hours or less, switch to Away mode. If your boiler does not have an Away mode, lower the set temperature to around 16°C.
  • When you will be out all day, turning the boiler off is the more economical choice.
  • The single most effective winter savings tip is to keep a steady indoor temperature of 18°C to 21°C. Maintaining a stable temperature tends to use less energy than repeatedly switching the boiler on and off.

For more detailed gas and heating cost saving tips, also check the guide How to Save on Boiler Gas Costs in Winter.

Boiler Cleaning

Running the boiler over a long period allows dust and debris to build up inside, meaning it needs more energy to reach the same temperature. Having a professional service and clean the boiler once every six months to a year improves efficiency and extends its lifespan. Intervals can vary depending on your situation; please verify the latest guidance with the Immigration Contact Center (1345) or your local Korea Immigration Service (KIS) office.

The figures and standards in this guide may change. For the latest information, check KMA Weather Nuri or the National Disaster Safety Portal, or contact your local Korea Immigration Service (KIS) office. You can also call 1345 for guidance.