Frozen Pipes: How to Prevent Them and What to Do If It Happens

Frozen pipes are one of the most preventable plumbing disasters, yet they cause an enormous amount of property damage every winter. When water inside a pipe freezes, it expands — and that expansion can split even a metal pipe, causing a flood when the pipe thaws. Understanding how and why pipes freeze, and what to do to prevent it, is one of the most practical things a homeowner in a cold climate can know.

Why Pipes Freeze

Water freezes at 32°F (0°C), but pipes are at greatest risk when outdoor temperatures drop to around 20°F (-7°C) or below and stay there for an extended period. The pipes most vulnerable to freezing are those with little or no insulation, exposed to exterior walls, located in unheated areas like crawl spaces or garages, and supply pipes in exterior walls or near exterior doors.

Pipes in warm interior walls rarely freeze, but pipes that run through uninsulated exterior walls, attic spaces, or crawl spaces are highly susceptible.

How to Prevent Frozen Pipes

Insulate exposed pipes: Foam pipe insulation sleeves are inexpensive and available at any hardware store. Wrap any pipes that run through unheated spaces — crawl spaces, garages, unfinished basement areas near exterior walls. This is the single most effective preventive step.

Let cold water drip from at-risk faucets: During extreme cold snaps, letting a thin trickle of water run from faucets served by exposed pipes keeps water moving. Running water is significantly harder to freeze than standing water.

Open cabinet doors under sinks on exterior walls: In very cold weather, opening cabinet doors under bathroom and kitchen sinks on exterior walls allows warm indoor air to circulate around the pipes.

Keep your home heated, even when away: If you are leaving your home for an extended period during winter, do not turn the heat off completely. Set the thermostat to a minimum of 55°F (13°C). The small cost of maintaining minimal heat is far less than the cost of burst pipe damage.

Seal gaps and cracks near pipes: Cold air that infiltrates through gaps around pipes where they pass through exterior walls dramatically increases the risk of freezing. Caulk or seal these gaps.

Know where your main water shutoff is: If a pipe does freeze and burst when it thaws, you need to be able to shut off the water immediately. Make sure everyone in your household knows where the main shutoff is and how to operate it.

Disconnect and drain garden hoses: Water left in a connected garden hose can back up into the outdoor faucet and the pipe behind it, freezing and causing damage. Disconnect hoses and drain outdoor spigots before the first freeze.

Install outdoor faucet covers: Foam outdoor faucet covers (sometimes called bib covers) insulate the outdoor spigot and the pipe just behind it. They attach with a simple strap and cost only a few dollars each.

How to Tell If a Pipe Is Frozen

Signs of a frozen pipe include:

• A faucet with no flow or very reduced flow during or after a cold spell
• Visible frost on an exposed pipe
• A strange smell from a faucet (frozen pipes can cause a pressure buildup that forces gases backward)
• A bulging section in an exposed pipe

If you have one faucet with no flow but other fixtures work normally, the frozen section is likely localized to the supply line for that fixture.

What to Do If a Pipe Freezes

Do not panic, but act carefully. First, open the affected faucet so that when ice begins to melt, water (and steam) can escape. The release of pressure is important — it reduces the risk of the pipe bursting.

Apply gentle heat. Safe methods for thawing a frozen pipe include:

• A hair dryer on low or medium heat, moved back and forth along the pipe
• An electric heating pad wrapped around the pipe
• Towels soaked in warm (not boiling) water wrapped around the pipe
• A portable space heater positioned near (but not directly against) the pipe

Work from the faucet end toward the frozen section. This allows water to escape as ice melts rather than building up pressure behind the thawing section.

Never use open flame. Propane torches, blowtorches, or any open-flame heat source should never be used on or near pipes. The risk of fire is serious, and the uneven, intense heat can also cause pipes to burst.

Check for damage after thawing. Once flow is restored, check the pipe carefully for any cracks or bulging that may have occurred during the freeze. A pipe that looks intact may still have a small crack that will open up under pressure.

When to Call a Plumber

• You cannot locate the frozen section
• The frozen pipe is inside a wall and not accessible
• The pipe has burst
• You have restored flow but notice any dripping, wet walls, or signs of water intrusion after the thaw
• You are not comfortable attempting the thaw yourself

A plumber can locate frozen pipes in walls using thermal imaging, thaw pipes safely with professional equipment, and assess whether any damage occurred that requires repair.

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The best time to prepare for frozen pipes is before the cold arrives. A few hours of insulation and preparation in the fall can prevent days of repairs and thousands of dollars in water damage. If you are in an area with cold winters and have not audited your pipe insulation, it is a worthwhile afternoon project.