Frozen Pipes: How to Thaw Them Safely and Keep Them From Bursting

Water expands as it freezes, and that expansion can split metal or plastic pipe. The damage often is not obvious until the ice melts and water starts pouring out of a crack inside a wall. That is why a frozen pipe deserves attention the moment you notice it, and why thawing it slowly and with the right tools matters as much as thawing it at all.

Signs a pipe is frozen

The American Red Cross advises suspecting a frozen pipe when you turn on a faucet and only a trickle comes out. Other clues:

• One fixture has no water while others in the house work normally.
• The cold side is affected but the hot side still runs (or the reverse), which points to a single frozen line.
• You can see frost on an exposed pipe, or a section feels much colder than the rest.
• The problem appeared after a night well below freezing, or after the heat was turned down.

If no fixture in the house has water, the freeze may be where the water service enters the home or at the meter, and you may need your water utility.

Find the frozen section

Pipes freeze where they are coldest. The Red Cross lists the usual suspects: pipes exposed to severe cold such as outdoor hose bibs and sprinkler lines, supply pipes in unheated areas like basements, crawl spaces, attics, garages and kitchen cabinets on exterior walls, and pipes that run along exterior walls with little insulation.

Start at the affected faucet and trace the supply line back toward where it enters the house. Feel along accessible pipe for the coldest spot and look for frost or a bulge. In many homes the culprit is a sink on an outside wall, with the pipe running through a cabinet that stays cold.

Check for a split before thawing. If you see a crack, a bulge or water already seeping, shut off the main water supply first. Thawing a cracked pipe with the water on turns a small problem into a flood.

Thaw the pipe step by step

1. Open the faucet the frozen pipe feeds, both hot and cold handles. As the ice melts, flowing water helps melt the rest and relieves pressure.
2. Apply gentle heat to the frozen section, working from the faucet end back toward the frozen spot so melting water has somewhere to go. The Red Cross lists safe options: an electric heating pad wrapped around the pipe, an electric hair dryer, a portable space heater kept away from anything flammable, or towels soaked in hot water.
3. Keep going until full pressure returns. A trickle means ice is still in the line.
4. Check every other faucet in the house. If one pipe froze, others in similar spots may have too.

Do not use a blowtorch, kerosene or propane heater, charcoal stove or any other open flame. Besides the fire risk inside walls and cabinets, overheating can damage pipe and fittings.

If the frozen section is inside a wall

Raise the thermostat, open cabinet doors on that wall, and aim a space heater or hair dryer at the wall area near the pipe, keeping a safe distance. If that does not restore flow within a reasonable time, or you cannot reach the frozen area, the Red Cross recommends calling a licensed plumber rather than cutting into the wall yourself.

Prevent it from happening again

Where	What to do
Outdoor hose bibs	Remove and drain hoses, close the indoor valve to the bib, then open the outside tap to let it drain
Pipes in garages, crawl spaces, attics	Add pipe insulation sleeves, or UL-listed heat tape or heat cable installed per its instructions
Sinks on exterior walls	Open cabinet doors during cold snaps so warm room air reaches the pipes
Very cold nights	Let cold water drip from faucets served by exposed pipes; moving water is much harder to freeze
Thermostat	Keep the same setting day and night during extreme cold
Leaving home in winter	Keep the heat on and set no lower than 55°F, as the Red Cross advises

Close garage doors if supply lines run through the garage, and add insulation to attics, basements and crawl spaces where pipes run. For a pipe that freezes every winter, rerouting it away from the exterior wall is the permanent fix.

Common mistakes

• Thawing with the faucet closed. Pressure builds between the ice and the closed valve.
• Leaving a space heater unattended near curtains, boxes or cleaning chemicals.
• Forgetting the outdoor bibs. A frost-free sillcock can still burst if a hose is left attached and traps water.
• Assuming no leak because the pipe looks fine. Check again once water is flowing; small cracks show up only under pressure.

When to call a plumber

Call a licensed plumber if the pipe has split or is leaking, if you cannot find or reach the frozen section, if flow does not return after thawing, or if the frozen pipe is inside a wall or ceiling. If water is leaking, shut off the main water valve first, then make the call. Burst pipes can damage drywall, flooring and insulation quickly, and many insurers want to know a professional made the repair.