Frozen pipe burst: what to do in the first hour

Why pipes burst when they freeze

Water expands as it freezes. In a pipe, that expansion builds pressure that metal and plastic both fail under, according to the American Red Cross. The break often shows up only when the ice thaws and full pressure returns, which is why many people discover a burst pipe the morning after a cold snap, not during it.

The pipes most at risk are the ones that sit in the cold: outdoor hose bibs, sprinkler and pool supply lines, supply lines in unheated basements, crawlspaces, attics, and garages, pipes inside kitchen and bathroom cabinets on outside walls, and any pipe running along an exterior wall with little insulation.

If the pipe has already burst

Speed matters because water keeps flowing until you stop it, and wet building materials start to support mold within a day or two. Work through these in order:

• Shut off the main water valve. It is usually where the water line enters the house, often in a basement, crawlspace, utility room, or near the water heater. Learn where it is before winter.
• If water is near outlets, appliances, or the electrical panel, turn off power to that area at the breaker, but only if you can reach the panel without standing in water. If you cannot, leave the house and call the utility.
• Open a faucet to drain the remaining water and relieve pressure in the lines.
• Take photos and video of the break, the water, and damaged belongings before you move or throw anything away. Your insurer will ask for them.
• Call a licensed plumber to repair the pipe, then call a water damage restoration shop for extraction and drying. Some shops do both; most do not.
• Move furniture and valuables off wet floors, and save receipts for anything you spend, including a hotel if you cannot stay home.

If a faucet only trickles: thawing a frozen pipe safely

A faucet that gives only a trickle in cold weather usually means ice in the line. The American Red Cross recommends keeping that faucet open, because flowing water helps melt the ice, and warming the frozen section with an electric heating pad, a hair dryer, a space heater kept away from anything flammable, or towels soaked in hot water.

Do not use a blowtorch, kerosene or propane heater, charcoal stove, or any open flame. Keep applying heat until full water pressure returns, then check the rest of the house: if one pipe froze, others on outside walls may have too. If you cannot find the frozen section, cannot reach it, or cannot thaw it, call a plumber.

What insurance usually covers

The Insurance Information Institute (Triple-I) says standard homeowners policies cover most damage that results from a freeze, including pipes that freeze and burst. Damage from a sudden, accidental burst is treated differently from damage that builds up over time from a slow leak, and flood or sewer backup water is excluded from most standard policies unless you added that coverage.

Coverage can be limited if the home was left unheated or vacant. Many policies limit or exclude coverage after a home has been unoccupied for a set period, often 30 to 60 days, and insurers can ask whether you took reasonable steps to keep the heat on. Your own policy language controls, so read the water and vacancy sections or ask your agent before you need them.

• Report the claim promptly and ask your insurer what they need before the restoration shop starts tearing anything out.
• Ask the restoration shop to document moisture readings and the drying plan. Adjusters often ask for it.
• Keep the damaged pipe section if the plumber removes it.

How to prevent frozen pipes

Most freeze damage is preventable with a few steps before and during cold weather. These come from American Red Cross and Triple-I guidance:

• Before the first freeze, disconnect and drain garden hoses, close the inside valves that feed outdoor hose bibs, and open the outside bibs so any water left can drain and expand.
• Drain sprinkler and pool supply lines following the installer's directions. Do not add antifreeze unless directed.
• Insulate pipes in attics, crawlspaces, basements, and garages. Pipe sleeves and UL-listed heat tape are made for this.
• Keep garage doors closed if water lines run through the garage.
• On very cold nights, open kitchen and bathroom cabinet doors on outside walls so warm air reaches the pipes, and let a faucet served by exposed pipes drip cold water.
• Keep the thermostat at the same temperature day and night during a cold snap instead of setting it back overnight.
• If you travel, leave the heat on. The Red Cross says no lower than 55°F; Triple-I suggests 65°F to keep the inside of walls from freezing. For a long absence, consider having the water system shut off and drained.

After the pipe is fixed: drying and mold

A repaired pipe does not mean a dry house. Water runs along framing, soaks into drywall and insulation, and pools under flooring and in wall cavities where you cannot see it. A restoration shop measures moisture with meters, removes what cannot be dried, and runs dehumidifiers and air movers until readings return to normal. Ask for those readings in writing.

If drying was slow or skipped, watch for a musty smell, stains that grow, or peeling paint in the weeks after. Those are signs to have the area checked for mold.