Quick answer
Pipes freeze when they sit in cold, unheated spaces such as exterior walls, crawlspaces and attics, especially during sustained cold with wind. Water expands as it turns to ice, and the pipe can split. Insulate exposed lines, let a faucet trickle on cold nights, keep the heat on, and know where the main shutoff is before a freeze.
What happened in January 2024
The Office of the Washington State Climatologist described the event as a week-long cold air outbreak that began on January 12, 2024. Its summary lists record-low daily temperatures at several stations. On January 12, Bellingham set a record low minimum of 3 degrees Fahrenheit. Bellingham, SeaTac and Olympia also set record low maximums that day, at 10, 25 and 30 degrees respectively. On January 13, Bellingham set a record low minimum of 7 degrees and a record low maximum of 19 degrees.
In Whatcom County, a news report from that Friday described the cold as driven by a northeast wind known as the Fraser Outflow. Gusts topped 50 mph in the northwest part of the county, overnight lows were nearly 30 degrees below normal for mid-January, and about 2,000 Puget Sound Energy customers were without power that morning, down from about 5,000 the night before.
In Snohomish County, the National Weather Service recorded 7 degrees in Arlington over the weekend of January 13 and 14, according to the Everett Herald. Lows were expected to stay around freezing until Thursday, which meant the cold lingered for days rather than a single night.
What the burst pipes looked like in Snohomish County
The Herald reported on January 15 that pipes burst at four Stanwood-Camano School District schools: Utsalady Elementary, Elger Bay Elementary, Stanwood Middle School and Port Susan Middle School. Utsalady, on Camano Island, was the only one set to stay closed the next day. In the Lake Stevens School District, Glenwood and Skyline elementary schools also had burst pipes and were set to close Tuesday. In the Edmonds School District, Meadowdale Elementary in Lynnwood closed Tuesday and Wednesday because of significant water damage throughout the building.
The Stanwood-Camano district said the pipes, especially those near or inside exterior walls, appeared to have been damaged by what it called "record-low sub-freezing temperatures recorded across the region." The district also reported damage to some books, office supplies and walls, but said vital equipment, computers and furniture were not harmed.
The Everett Fire Department responded to 27 service calls from Sunday afternoon to Monday afternoon, and the Herald reported that most involved broken water pipes.
Why pipes in exterior walls and crawlspaces freeze
The detail the district pointed to, pipes near or inside exterior walls, is the most common weak point in houses as well as schools. A pipe in an interior wall is surrounded by heated rooms. A pipe in an exterior wall may have only a thin layer of insulation between it and outdoor air, and sometimes none. The same holds for pipes in crawlspaces, attics, garages and along the underside of floors over unheated spaces.
Water expands as it freezes. When ice forms in a pipe, the pressure can split the pipe wall or push a fitting apart. Plumbers often note that a split pipe may not leak while it is frozen, because ice is plugging the opening. The leak shows up when temperatures rise and the ice melts. That is one reason damage is often discovered during the thaw rather than during the freeze.
Wind and duration matter. Moving air pulls heat from exposed surfaces and can push cold air through gaps around crawlspace vents, rim joists and wall penetrations. A sustained northeast wind like the one reported in Whatcom County is harder on exposed pipes than calm air at the same temperature. In general, a pipe that survives one cold night may not survive several, because the surrounding materials keep losing heat. This is an explanation of how heat loss works, not a finding drawn from the January 2024 reports.
Prevention steps from emergency management
The Snohomish County Department of Emergency Management publishes guidance on protecting pipes. Its recommendations, summarized below, are practical and inexpensive compared with a flooded room.
- Insulate the pipes most likely to freeze, such as those near outside walls, in crawl spaces or in the attic, and consider UL-approved heat tape.
- Seal gaps that let cold air reach pipes.
- Disconnect garden hoses, and shut off and drain the pipes that feed outdoor faucets.
- On cold nights, let hot and cold water trickle from a faucet on an outside wall.
- Open cabinet doors so warm air reaches pipes under sinks and near appliances on outer walls.
- Keep the heat on, set no lower than 55 degrees.
- If you will be away, have someone check daily that the heat is working, or drain and shut off the water system.
If a pipe freezes or bursts
Emergency management guidance says every household member should know how to shut off the water, since stopping the flow limits damage. After that, call a plumber and an insurance agent. A KATU report on pipe protection says to close the main shutoff valve right away if a pipe bursts, and notes that it may be indoors or outdoors.
Thawing needs care. The county guidance says never to try to thaw a pipe with an open flame or torch. KATU adds that water in the pipe can boil and cause it to explode, and suggests towels soaked in hot water wrapped around the pipe, an electric heating pad or an electric hair dryer. The county also warns of electric shock risk around standing water, so stay away from outlets and appliances if water is on the floor.
Opening the affected faucet before thawing lets water flow as soon as the ice clears. If several fixtures on the same line run dry, the blockage is likely farther upstream, often in a wall or crawlspace that cannot be seen.
After the thaw: check for hidden leaks
Because a split pipe can stay sealed by ice, a freeze is not over until the pipes have thawed and been checked. Look at ceilings below bathrooms and kitchens, walls near exterior corners, and the crawlspace for dripping or damp insulation. A simple test helps: turn off every fixture and appliance, then watch the water meter. If it keeps moving, water is leaking somewhere in the house.
Pipes that freeze repeatedly in the same spot point to a design problem rather than bad luck. A run of supply line that sits in an exterior wall, or a bathroom plumbed along a cold outside edge, may justify rerouting or better insulation rather than a series of patch repairs.
When to call Pyper Plumbing
A burst pipe with water running is an emergency, and the first step is still to close the main shutoff. Pyper repairs frozen and burst pipes, finds hidden leaks after a thaw, and handles repiping where sections of old or poorly placed pipe keep failing. It serves Snohomish, Skagit, Whatcom and Island counties.
If pipes froze but nothing leaked, an inspection before the next cold forecast is a reasonable precaution, especially for lines in exterior walls and crawlspaces. Heating system problems are a separate matter, since Pyper does not do HVAC or electrical work.
Common questions
Why do pipes in exterior walls freeze first?
They sit close to outdoor air with little insulation between them and the cold, while pipes in interior walls are surrounded by heated rooms. The Stanwood-Camano School District said pipes near or inside exterior walls appeared to be among those damaged in January 2024. Crawlspaces, attics and garages pose the same risk.
Should I let faucets drip during a freeze?
Snohomish County emergency management advises letting hot and cold water trickle from a faucet on an outside wall during cold nights, and opening cabinet doors so warm air reaches pipes under sinks. A drip does not guarantee protection, so insulation and keeping the heat on matter as well.
What should I do first if a pipe bursts?
Close the main water shutoff to stop the flow, and stay away from electrical equipment if there is standing water. Then call a plumber and your insurance agent. Do not use an open flame to thaw any pipe.
Sources
Facts in this guide come from the following references. Local rules and manufacturer instructions can differ, so follow your utility and your equipment manual.
- Frozen, burst pipes close schools in Lake Stevens, Camano, Edmonds (HeraldNet)
- Fierce winds knock out power as record-breaking cold grips Whatcom County (Yahoo News)
- Office of the Washington State Climatologist, monthly summary PDF (University of Washington)
- Water Pipes (Snohomish County Department of Emergency Management)
- Protect your pipes: How to prepare your home for winter weather (KATU)
This guide is general information, not a substitute for an on-site inspection. If you smell natural gas, leave the building and call 911 or your gas utility. Pyper does not perform gas line work.
