Frozen pipes: prevention, thawing and what happens when they burst

Which pipes freeze first?

The pipes that freeze are the ones that see the cold. The American Red Cross lists three groups: pipes exposed to severe cold, such as outdoor hose bibs, pool supply lines and sprinkler lines; supply pipes in unheated interior areas like basements, crawl spaces, attics, garages and under kitchen cabinets; and pipes that run against exterior walls with little or no insulation.

Hot water lines freeze too. Texas A&M AgriLife Extension notes that a hot supply line freezes just like a cold one when water is not moving through it and the pipe sits in cold air.

Southern homes are not exempt. Builders in warm climates often run pipes through uninsulated attics and crawl spaces, precisely the spots that freeze during a rare cold snap. That is why a Texas or Florida freeze bursts so many pipes in a single night, and why one frozen pipe is a warning to check the rest of the house.

At what temperature do pipes freeze?

Water freezes at 32F, but a pipe inside a building has the structure around it as a buffer. The widely used rule of thumb: Texas A&M AgriLife Extension says water pipes have the potential to freeze and burst when the outside temperature reaches 20F or below. Treat roughly 20F as the alert threshold for homes without protected plumbing.

The threshold is not a guarantee either way. Wind pushing cold air into a vented crawl space or an attic can freeze a pipe at milder temperatures, and a well-insulated pipe can ride out a colder night. Duration matters too: a brief dip to 20F is less dangerous than a day below freezing. When a hard freeze is forecast, act on the prevention steps below rather than betting on the thermometer.

How do you keep pipes from freezing?

Prevention is cheap and mostly takes one evening. The Red Cross and Texas A&M AgriLife Extension recommend the same core steps.

Before winter: drain sprinkler and pool supply lines per the manufacturer’s directions, and do not add antifreeze unless directed. Disconnect and drain garden hoses, close the indoor valves that feed outdoor hose bibs, and leave the outdoor valves open so trapped water can expand without breaking the pipe. Insulate pipes in unheated areas with foam pipe sleeves, or install UL-listed heat tape or heat cable.

During a cold snap: let cold water drip from faucets served by exposed pipes. The Red Cross says running water through the pipe, even at a trickle, helps prevent freezing. Open kitchen and bathroom cabinet doors so warm air reaches plumbing on exterior walls. Keep the garage door closed if supply lines run through it.

Thermostat: keep it at one steady setting day and night, and if you leave home, no lower than 55F (Red Cross). The extra heating cost is small next to a burst-pipe claim.

How do you thaw a frozen pipe safely?

Suspect a frozen pipe when a faucet gives only a trickle. Common freeze points are pipes against exterior walls and where the water service enters through the foundation (Red Cross).

First, keep the faucet open. Water moving through the pipe as you work helps melt the ice. Second, find the main shutoff valve before you start: the pipe may already be split, and it will leak the moment it thaws (Texas A&M AgriLife Extension).

Then apply heat to the frozen section, working from the faucet back toward the blockage. The Red Cross lists four safe heat sources: an electric heating pad wrapped around the pipe, an electric hair dryer, a portable space heater kept away from flammable materials, or towels soaked in hot water. Keep electrical cords away from any water. Keep applying heat until full pressure returns, then check every other faucet in the house, because one frozen pipe often means more.

Never use an open flame. The Red Cross is explicit: no blowtorch, kerosene or propane heater, charcoal stove or other open flame device. If you cannot locate the frozen section, cannot reach it, or cannot thaw it, call a licensed plumber.

Where is the water shutoff valve?

The main shutoff is usually where the water line enters the house: in the basement or crawl space on the street-facing wall, in the garage near the water heater, or outside in a covered box near the foundation or at the property line by the meter. Inside valves are typically a round gate wheel (turn clockwise to close) or a lever ball valve (turn a quarter turn so the handle sits across the pipe).

Find it now, tag it, and make sure everyone in the house can close it. When a pipe bursts, minutes of flow decide whether you are drying a carpet or replacing ceilings. If the only shutoff is at the meter, you may need a meter key or curb key; check before the freeze, and call the utility if the meter valve will not turn.

What do you do when a frozen pipe bursts?

Shut off the main water valve immediately, then open faucets to drain pressure from the lines. If water is near outlets, fixtures or the electrical panel, cut power to the affected area at the breaker before stepping in. Then move to drying: water spreads fast and soaks drywall, insulation and flooring.

Our burst pipe guide walks through the full first-hour response, and the water damage hub covers mitigation and repair. The clock that matters most is the drying window: EPA says to dry wet materials within 24 to 48 hours to prevent mold growth. For how long full structural drying takes, see drying time, and for who to call, see water mitigation vs restoration.

Photograph everything before you throw anything away, and keep the split pipe section if a plumber cuts it out. The damaged pipe is physical evidence for the claim.

Does insurance cover frozen and burst pipes?

Generally yes for the resulting water damage, with one important condition. The standard ISO HO-3 homeowners form covers freezing of a plumbing, heating, air conditioning or sprinkler system, and the discharge that follows, but only if you used reasonable care to maintain heat in the building, or shut off the water supply and drained the systems and appliances. Triple-I says standard homeowners policies will cover most of the kinds of damage that result from a freeze, burst pipes included.

In practice that means the sudden and accidental water damage, torn-out drywall, ruined flooring and the cost of accessing the broken pipe, is typically covered, while the burst pipe section itself and gradual seepage often are not. Leaving a house unheated with the water on is the classic way a claim gets denied under the heat-maintenance condition. If you winter elsewhere, keep the heat at 55F or more, or shut off and drain the water, and keep proof, such as smart thermostat logs or a plumber’s winterization receipt.

We explain how these policies work; whether your claim is covered depends on your policy and facts. Check your declarations page and ask your insurer, your state insurance department, a licensed public adjuster or an attorney. See water damage coverage and documenting your claim.