Frozen Pipes: How to Prevent Them, Thaw Them Safely, and What to Do If One Bursts
Published 8/13/2026
The short answer: Pipes freeze when water inside them turns to ice, and they burst not because of the ice itself but because of the pressure that builds between the ice blockage and a closed faucet.[2] The most vulnerable pipes are those in unheated spaces and against exterior walls. You can prevent most freezes by keeping heat on, letting exposed faucets drip, and insulating pipes — and if one does freeze, you can often thaw it safely with gentle heat, never an open flame.[1] If a pipe bursts, the single most important move is to shut off your main water supply immediately.
Why pipes freeze — and why they burst
Water is unusual: it expands as it freezes. As the American Red Cross explains, "this expansion puts tremendous pressure on whatever is containing it, including metal or plastic pipes."[1] But the burst usually is not where the ice forms. Research from the University of Illinois Building Research Council found that as freezing continues, water pressure rises downstream — in the section of pipe between the ice blockage and a closed faucet — and it is that trapped pressure that ruptures the pipe, often at a spot with little or no ice.[2] That is exactly why letting a faucet drip helps: it relieves the pressure.
Which pipes are most at risk
The Red Cross identifies three high-risk groups: outdoor-exposed pipes such as hose bibs, pool supply lines, and sprinkler lines; water supply pipes in unheated interior areas like basements, crawl spaces, attics, garages, and kitchen cabinets; and pipes that run against exterior walls with little or no insulation.[1] Homes in normally mild regions are especially vulnerable because their pipes are more often located outside the building's insulation.[2]
As for how cold it has to get, field testing by the University of Illinois Building Research Council found that uninsulated pipes in unconditioned spaces began freezing when the outside temperature fell to about 20°F — a figure often cited as a "temperature alert threshold."[2] Consumer Reports notes freezing "generally occurs below 20°F," while cautioning it can happen above that in poorly insulated spaces.[4]
How to prevent frozen pipes
Let exposed-pipe faucets drip. Even a trickle of running water relieves pressure and helps prevent a freeze.[1][4]
Keep the thermostat steady, day and night. A consistent temperature is worth more than a lower nighttime setting during a cold snap.[1]
Open cabinet doors under sinks on exterior walls so warm room air can reach the plumbing.[1]
Keep the garage door closed if water lines run through the garage.[1]
Disconnect and drain garden hoses, close the inside valves that feed outdoor hose bibs, and drain those lines.[1]
Insulate the pipes most at risk with foam pipe sleeves or heat tape, and add insulation to attics, basements, and crawl spaces.[1]
If you travel in winter, keep the heat on — the Red Cross advises setting it no lower than 55°F while you are away.[1] (Some insurers suggest a more conservative floor; the Insurance Information Institute recommends keeping the house heated to a minimum of about 65°F in severe cold.[5])
Insulation is inexpensive insurance. Foam pipe sleeves cost only a few dollars per length, and the Insurance Information Institute also suggests replacing washing-machine and other supply hoses every five to seven years and installing an emergency pressure-release valve to guard against freeze-driven pressure.[6]
How to thaw a frozen pipe safely
If you turn on a faucet and only a trickle comes out, a pipe is likely frozen. To thaw it:
Keep the faucet open. As the ice melts, running water through the pipe helps melt the rest.[1]
Apply gentle heat to the frozen section using an electric heating pad wrapped around the pipe, an electric hair dryer, hot towels, or a portable space heater kept away from anything flammable. Keep applying heat until full water pressure returns.[1]
Never use an open flame. The Red Cross is explicit: "Do not use a blowtorch, kerosene or propane heater, charcoal stove, or other open flame device."[1] Open flames are a fire and carbon monoxide hazard and can damage the pipe.
Call a licensed plumber if you cannot locate or reach the frozen section, or if it will not thaw.[1]
What to do if a pipe bursts
A burst pipe can release a large amount of water quickly, so speed matters:
Shut off the main water supply immediately. Know where your main shutoff valve is before an emergency — it is usually at the water meter or where the main line enters the house.[4][7]
Open faucets to drain remaining water from the system and relieve pressure.
Call a licensed plumber for the repair.
Document the damage with photos and notes for an insurance claim before you clean up.
Will insurance cover it?
Usually, yes — with an important catch. Standard homeowners policies cover damage from a "sudden and accidental" discharge from a plumbing system, which includes a burst pipe.[3] The Texas Department of Insurance confirms this coverage "pays for damage from burst pipes."[7]
The catch is neglect. The National Association of Insurance Commissioners notes that "if your insurance company determines you neglected your plumbing system by not taking preventative measures to avoid freezing, the damage from a burst pipe may not be covered," and policies "generally require homeowners to maintain the home at a minimum temperature, or shut off the water supply if the home is vacant."[3] In other words, keeping the heat on is not just good practice — it can be the difference between a covered claim and a denied one. (Note that flood insurance does not cover burst pipes; that is a separate policy for a different peril.[7])
What repairs and prevention cost
Pricing varies by region, pipe location, and how much water damage occurred, but as a planning range:
Item
Typical cost
Burst pipe repair
~$500 average; roughly $150 for a small section to $5,000+ for complex jobs[8]
Resulting water-damage repair
~$4–$7 per square foot[8]
Pipe insulation (whole-home)
~$360–$850; about $0.50–$5 per linear foot by material[9]
Because roughly 80% of a burst-pipe repair bill is labor,[8] a few dollars of foam sleeves on your most exposed pipes is one of the cheapest forms of protection a homeowner can buy.
Frequently asked questions
Should I leave faucets dripping all winter?
No — only during hard freezes, and only the faucets served by pipes that run through unheated or exterior-wall spaces. A slow drip relieves the pressure that actually bursts pipes.[1][2]
My pipe is frozen but hasn't burst — is it an emergency?
Act promptly but calmly. Keep the faucet open and apply gentle heat to thaw it; the longer it stays frozen, the more pressure can build. If you cannot reach or thaw it, call a plumber.[1]
What temperature should I keep the house at when I travel?
The Red Cross recommends no lower than 55°F while you are away; some insurers advise a higher floor around 65°F in severe cold. Whatever you choose, keeping heat on may also be required for a burst-pipe claim to be covered.[1][3][5]