Frozen Pipes: How to Thaw Them Safely and Prevent a Burst

You turn on a tap on a bitter-cold morning and get a sad little trickle — or nothing at all. That's the unmistakable sign of a frozen pipe, and it sits in an awkward middle ground: it isn't a flood yet, but it's a flood waiting to happen. Handle it calmly in the next hour and you'll likely be fine. Reach for a blowtorch, or just wait and hope, and you risk turning a frozen pipe into a burst one.

This guide is the emergency middle: what to do right now when a pipe is frozen but hasn't burst. (For getting ahead of it next time, see how to prevent frozen pipes; for the worst case, burst pipe — do these 6 things.)

Quick answer: Open the faucet the frozen pipe feeds, then warm the frozen section with a hair dryer, heating pad, or space heater — working from the faucet end toward the cold spot — until water runs at full pressure. Never use an open flame. If you spot a crack or bulge, shut off your main water valve before thawing, and if you can't reach the freeze, call a plumber.

Why a frozen pipe is an emergency, not an inconvenience

Water is strange stuff: it expands as it freezes. According to the American Red Cross, that expansion "puts tremendous pressure on whatever is containing it" — and "no matter the strength of a container, expanding water can cause pipes to break." A solid plug of ice doesn't usually split the pipe where the ice is. Instead it traps a pocket of water between the ice and a closed faucet, and that trapped water is what gets squeezed until the pipe ruptures, often somewhere downstream of the ice itself.

That's the whole logic behind every step below. Relieve the pressure (open the faucet), melt the ice gently (steady heat), and watch the thaw (where leaks reveal themselves). For context on why this matters so much: water damage and freezing is consistently one of the most common home insurance claims — the Insurance Information Institute puts it at roughly one in 60 insured homes filing a water or freezing claim every year, the second-largest claim category after wind and hail.

Step 1 — Confirm it's frozen, and find the section

If a faucet gives only a trickle or nothing during cold weather, suspect a freeze before anything else. The pipes that freeze first are predictable — the Red Cross lists them clearly:

• Outdoor and exposed runs — hose bibs, pool supply lines, sprinkler lines.
• Pipes in unheated interior spaces — crawl spaces, attics, garages, and the cabinets under kitchen and bathroom sinks.
• Pipes against exterior walls with little or no insulation.
• Where the water service enters through the foundation.

To pinpoint it, start at the dead faucet and trace its line backward toward those weak spots. The frozen section is usually noticeably colder than the rest of the pipe, may show frost on the outside, and can bulge slightly. Run your hand along the run — the spot that makes your fingers ache is almost always it. If the pipe vanishes into a wall, the wall or cabinet it's behind is your clue.

Frozen, or something else?

A few look-alikes are worth ruling out so you don't heat the wrong thing.

Step 2 — Open the faucet (do this before you apply any heat)

Open both the hot and cold handles on the affected fixture. This is the single most important move and people skip it. As the Red Cross puts it: "Keep the faucet open. As you treat the frozen pipe and the frozen area begins to melt, water will begin to flow… running water through the pipe will help melt ice." Just as important, the open faucet gives the trapped, pressurized water somewhere to go — which is exactly what stops the pipe from bursting as it thaws.

One exception: if you already see a crack, a bulge, or water where it shouldn't be, the pipe may have failed. In that case, shut off the main water valve first, then thaw — a damaged pipe will gush the moment the ice melts and the faucet won't be enough to save you.

Step 3 — Apply gentle, steady heat (and never an open flame)

Now warm the frozen section. The Red Cross–endorsed methods are all about slow, even heat:

• A hair dryer on low-to-medium, waved back and forth along the pipe.
• An electric heating pad wrapped around the pipe.
• A portable space heater aimed at the area — kept well clear of anything flammable.
• Towels soaked in hot water wrapped around the pipe and re-warmed as they cool.

Always work from the faucet end toward the coldest spot. That way the melt water drains out the open faucet instead of getting trapped behind more ice and building pressure. For a pipe inside a wall you can't reach directly, warm the room: open cabinet doors, point a space heater at the wall, and be patient — indirect heat takes longer but it's safe.

Why the hard rule against flame? Concentrated, extreme heat can boil trapped water to steam and rupture the pipe, scorch or ignite the surrounding wall and insulation, and an indoor combustion device produces carbon monoxide. Slow heat is what thaws a pipe without breaking it.

Step 4 — Restore pressure, then check everything

Keep applying heat until water flows at full pressure. Then do two things:

1. Check every other faucet in the house. The Red Cross is blunt about this: "If one pipe freezes, others may freeze, too." Run the hot and cold at each fixture briefly to confirm.
2. Watch the thawed section for leaks over the next hour. The pipe survived being frozen; make sure it survived the thaw. A bead of water at a joint or a damp spot on drywall means a small split that's better caught now.

If pressure doesn't come back, or you never could reach the frozen section, stop and call a licensed plumber. A pipe frozen deep in a wall or under a slab is past the point of DIY, and forcing it risks the burst you're trying to avoid.

What it costs — thawing vs. the burst it prevents

The math here is lopsided, which is the whole point of acting fast.

Don't let it happen again

Once everything's flowing, take 20 minutes to make sure you're not back here next week. The full playbook is in how to prevent frozen pipes and how to insulate pipes, but the high-value moves are:

• Insulate the run that just froze with foam pipe sleeves — cheap, and it targets the exact spot you now know is vulnerable. For a stubborn cold spot, add UL-listed heat tape.
• Let that faucet drip during the next hard freeze. A pencil-lead stream of moving water resists freezing and relieves pressure.
• Open cabinet doors under sinks on exterior walls so room heat reaches the pipes, and keep the heat on at a steady temperature day and night — never below about 55°F if you're away.
• Seal the draft that's chilling the pipe — a gap in the rim joist or around a foundation penetration lets freeze-line cold air hit the pipe directly.
• Disconnect and drain outdoor hoses and close interior hose bib shutoffs before winter.
• Know where your main water shutoff is — and test it — so if a pipe ever does burst, you can stop the flood in seconds, not minutes.

One thing pros do that homeowners don't: before a deep cold snap, they think about the coldest, most-forgotten corner of the house — the crawl space, the garage wall, the bathroom on the north side — and protect that one first. Freezes almost always start at the same weak spot. Fix it once and you stop fighting it every winter.

When to call a plumber

Thaw it yourself when the pipe is accessible and intact. Call a pro when:

• You can't find or reach the frozen section (inside a finished wall, under a slab, deep in a crawl space).
• Several hours of steady heat doesn't restore flow.
• You see a split, bulge, or leak — especially if it's already burst and you've had to shut off the main.
• Multiple pipes are frozen and you're racing the cold.

There's no shame in it — a $200 service call is cheap insurance against a five-figure water-damage claim.

Sources

• American Red Cross — Preventing & Thawing Frozen Pipes
• Insurance Information Institute — Facts + Statistics: Homeowners and Renters Insurance