Frozen Pipes: What to Do Before They Burst
Open the affected faucet, then apply gentle heat starting at the faucet end and working back toward the frozen section. Never use an open flame. Know where your main shutoff is before you start, because a split hidden by ice only reveals itself when the ice clears.
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Recognizing a frozen pipe
The signature symptom is one fixture producing nothing, or a thin trickle, while other fixtures run normally. That localization is what distinguishes a frozen branch from a supply problem: if the whole house has no water during a freeze, the blockage is likely at the meter or in the buried service line, which is the utility's problem rather than a job for a hair dryer.
Look at where the affected fixture's supply runs. Exterior walls, unheated garages, crawlspaces, attics, and rim joists are where it will be.
Thawing it safely
The sequence matters. Opening the faucet first gives melting water and released pressure somewhere to go, and working from the faucet end backward means the meltwater can escape rather than being trapped behind more ice.
Locate your main shutoff first
Before applying any heat, know exactly where the valve is and confirm you can operate it. The pipe may already be split.
Open the affected faucet
Open both hot and cold sides. This relieves pressure and gives you a visible signal when flow returns.
Apply gentle heat from the faucet end
Use a hair dryer, a heat lamp, a space heater, or towels soaked in hot water. Work from the fixture toward the frozen section, not the reverse.
Never use an open flame
No torches, no propane heaters aimed at framing. Thawing pipes with a torch is a well-documented cause of house fires every winter.
Watch as flow returns
Stay at the fixture. If water appears anywhere it should not, shut the main immediately.
Warm the space, not just the pipe
Open cabinet doors, run a space heater in the room, and let heat reach the whole run. One thawed section in a cold cavity refreezes.
If you cannot reach the frozen section
Pipe inside a finished wall or under a slab is beyond a hair dryer. Raising the temperature of the whole space helps, and sometimes that is enough given time, but a plumber has pipe-thawing equipment that works where you cannot reach.
A frozen buried service line is a different matter entirely. Homeowners cannot address it and neither, usually, can a plumber; the water utility thaws those. If your whole house lost water during a freeze, call the utility before you call anyone else.
Preventing the next one
The run that froze this time will freeze again in the next comparable cold, because the exposure has not changed. Insulating that specific run, adding heat trace, or rerouting it out of the cold cavity is what actually fixes the problem.
During cold snaps, the cheap measures genuinely work: let vulnerable fixtures drip, open cabinet doors on exterior walls, keep the thermostat steady rather than setting back overnight, and disconnect outdoor hoses. A hose left connected to a bibb over winter is one of the most reliable ways to split a pipe inside the wall behind it.
Frequently asked questions
At what temperature do pipes freeze?
Exposed pipe generally starts to be at risk when outdoor temperatures fall to about 20°F, though the pipe's location matters far more than the number. A well-insulated pipe in conditioned space survives days of that; an uninsulated pipe in a windy exterior wall cavity can freeze in a few hours at the same temperature.
Does letting the faucet drip really help?
Yes, for two reasons. Moving water is harder to freeze, and more importantly an open faucet prevents the pressure buildup between an ice plug and a closed valve that is what actually splits pipes. A pencil-thin stream from the fixture furthest along the vulnerable run is enough.
How long until a frozen pipe bursts?
There is no reliable clock. Some pipes freeze solid and never split; others fail within hours. It depends on how much water is trapped, how fast the freeze progresses, and the pipe's material and condition. PEX tolerates freezing far better than rigid copper, which is one reason it dominates repiping today.
Should I turn the heat up during a cold snap?
Keep it steady rather than high, and do not set it back overnight during a hard freeze. The overnight setback is exactly when pipes freeze, and the small heating saving is not worth the risk. If you are leaving town in freezing weather, keep the thermostat at 55°F minimum and have someone check the house.
Related guides
- How to Shut Off Your Water in an EmergencyFind and operate your main water shutoff before you need it. The single most valuable thing a homeowner can know during a plumbing emergency.
- What to Do When a Pipe BurstsThe first ten minutes after a pipe bursts determine most of the damage. Here is the order of operations that limits it.
- Winterizing Your PlumbingThe autumn work that prevents the winter emergency, and the full winterization procedure for properties left vacant in freezing weather.
- Overflowing Toilet: Stop It in Under a MinuteHow to stop an overflowing toilet immediately, and how to tell whether the problem is the toilet or the main sewer line.
Related services
- Frozen Pipe Thawing and RepairProfessional thawing of frozen supply lines, plus inspection and repair of any sections that split while frozen.
- Emergency Burst Pipe RepairA burst pipe releases water continuously until the supply is shut off. Emergency repair covers isolation, pipe section replacement, and pressure testing.
- Main Water Line RepairRepair and replacement of the buried water service line between the meter and the house, including trenchless replacement options.
Cost guides
- How Much Does an Emergency Plumber Cost?What emergency plumbing actually costs, how after-hours premiums work, and which problems are cheaper to schedule for morning.
- After-Hours Plumbing Rates ExplainedWhat the overnight, weekend, and holiday premiums actually are, and how to decide whether tonight's problem justifies paying them.
- Burst Pipe Repair CostWhat burst pipe repair costs by location and pipe type, plus the water damage costs that usually exceed the plumbing.
Common questions
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