Frozen Pipes: Thaw Them Safely & Keep Them From Bursting
If a faucet runs to a trickle in a cold snap, a pipe is frozen, not yet burst. Open that faucet, then warm the pipe starting at the faucet end and working toward the cold spot, with a hair dryer or heat tape, never an open flame. Find the freeze in exterior walls, crawl spaces, and attic runs. Prevention is cheap: insulation and a $50 – $300 heat cable beat a burst pipe every time.
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Safety first: if you smell gas, see water near electrical outlets or your panel, or sewage is contacting living areas, get people clear first. For a gas smell, leave and call 911 or your gas utility's emergency line before anything on this page.
- !A pipe has already burst and water is spraying or flooding: shut off the main water valve immediately
- !Water from a burst or thawing pipe is reaching outlets, the panel, or any wiring: cut power at the breaker first
- !You see a bulged, split, or cracked section of pipe: it will release when it thaws, so shut the main before warming it
- !A frozen pipe is near electrical equipment and you are about to apply heat: kill that circuit before introducing any water risk
- !The smell of gas anywhere near where you are working: leave and call the gas utility from outside, do not apply heat
- ✓Open the affected faucet before thawing: running it gives melting ice somewhere to go and relieves pressure
- ✓Locate the frozen section: trace from the dead faucet back along the pipe to a cold spot, often frosted or bulged
- ✓Apply gentle heat from the faucet end toward the freeze: a hair dryer, heat tape, hot towels, or a space heater nearby
- ✓Open cabinet doors under sinks on exterior walls to let household warmth reach the pipes
- ✓Keep a pencil-thin trickle running from vulnerable faucets during hard freezes: moving water resists freezing
- →You cannot locate the frozen section, or it runs inside a finished wall you cannot reach
- →A pipe has thawed and is now leaking, or you suspect a hidden split that will leak when it warms
- →Multiple pipes are frozen or the freeze keeps recurring in the same spot each winter
- →You want heat cable, pipe insulation, or rerouting installed on lines that freeze every year
- →An outdoor faucet or its supply line froze and the sillcock now leaks or will not shut off
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Thaw it safely
First, open the frozen faucet, both the hot and cold handles. As the ice melts, the water needs somewhere to escape, and an open tap relieves the pressure that actually bursts pipes. A trickle starting to flow is your sign the thaw is working.
Then heat the pipe, and direction matters: start at the faucet end and work back toward the frozen section, never the reverse. Warming the middle first can trap melting water behind ice still plugging the line, and that trapped, expanding water is exactly what splits pipes. A hair dryer, electric heat tape, hot wet towels, or a space heater set a safe distance away all work. Apply heat steadily and patiently; a stubborn freeze can take a while.
One absolute rule: never use an open flame. A propane torch, a heat gun on high, or any blowtorch can scorch framing, start a fire inside a wall, and overheat the pipe. Plenty of house fires start exactly this way. Heat tape and a hair dryer are slower, and that is the point. If the pipe is somewhere you cannot safely reach or warm, that is a call, not a place to improvise with fire.
Find the freeze
Pipes freeze where the cold reaches them, which is a short list of usual spots. Exterior-wall runs are the most common: a pipe in an outside wall has little insulation between it and a sub-freezing night. Unheated crawl spaces and basements are next, along with pipes in attics and along the underside of floors over vented areas. Garages with water lines, and any line near a draft from a vent or a gap in the sheathing, round out the list.
Trace from the faucet that stopped working back along its supply pipe and look for the cold zone: a section that is frosted over, sweating, or noticeably colder to the touch, sometimes already bulged. That is where to apply heat. If the dead faucet is on an exterior wall, the freeze is almost certainly in that wall or just below it. Knowing the likely spots turns thawing from a guessing game into a targeted job.
If it already burst
A frozen pipe that has split will not show it until it thaws, then it releases all at once. If you find a bulged or cracked section, or water is already flowing, shut off the main water valve to the house before doing anything else, and cut power to any circuit the water can reach. Stopping the supply is what limits the flood; the repair comes after.
A burst line is a real repair, not a thaw-and-go. Most freeze-bursts happen on supply lines in exterior walls, and getting at them often means opening drywall. Our burst pipe repair cost page covers what the repair and cleanup run, and if the split is inside a wall, a pipe leaking in a wall walks through locating it before anyone cuts. The faster you kill the main, the smaller the repair and the cleanup.
Prevention that works
A few habits stop most freezes. During a hard freeze, run a pencil-thin trickle from faucets fed by vulnerable pipes, especially those on exterior walls; moving water is far harder to freeze. Open the cabinet doors under exterior-wall sinks so household heat reaches the pipes. Keep the house at a steady temperature day and night, and if you travel in winter, do not drop the thermostat below the mid-50s.
For the lines that freeze every year, fix them rather than babysit them. Foam pipe insulation sleeves are a few dollars and go on in minutes. Electric heat cable (heat tape) wraps a vulnerable run and warms it on a thermostat: a typical kit runs $50 – $300 depending on length and whether it is self-regulating. In crawl spaces, closing foundation vents for winter and insulating the space keeps the whole area above freezing. These are small costs against a four-figure burst-pipe cleanup.
Outdoor faucets and what temperature matters
Outdoor faucets freeze and burst the supply pipe behind them, and the damage often shows up indoors when the line thaws. Before winter, disconnect and drain hoses, shut off the interior valve feeding each hose bib if you have one, and open the outdoor faucet to drain it. A frost-proof sillcock is the durable upgrade, since its shutoff sits back inside the heated wall; replacing a freeze-prone spigot with one is covered on our hose bib replacement cost page.
As for the cold itself: pipes generally start to freeze when sustained outdoor temperatures drop to around 20°F, but the number is not the whole story. Wind chill matters for pipes in exterior walls and unheated spaces, because moving cold air pulls heat out faster and can freeze a line the still-air temperature alone would not. An exposed pipe in a windy crawl space can freeze well before a sheltered one does, which is why the vulnerable-spot list matters more than the thermometer reading.
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