How to Thaw a Frozen Pipe

One faucet gives nothing, or a thin trickle, while the rest of the house runs normally. That points to a plug of ice in one run of pipe, usually along an exterior wall, in a crawlspace, or in an unheated garage, and frost or a slight bulge on the pipe confirms it. What most people miss is that the pipe may already be split, and a split reveals itself only once the ice melts and water starts moving again.

Open the affected faucet first

Open both handles on the fixture that is dead and leave them open the entire time. Melt water needs a route out, and the pressure that builds as the ice plug lets go needs somewhere to release. A closed faucet turns a thawing pipe into a sealed tube.

Locate the main shutoff before applying any heat

Know where the main valve is and confirm it turns before you warm anything, because a split pipe starts flooding the moment the ice clears. If the valve is unfamiliar, read how to shut off the water to a burst pipe first.

Trace the line and find the frozen section

Follow the dead line back from the fixture toward where water enters the house. Run a hand along it. The frozen stretch is colder than the rest, sometimes frosted, and it almost always sits where the pipe crosses an unheated space.

Warm the pipe with safe heat, never a flame

Never use a blowtorch, a propane torch, or any open flame on a pipe. Thawing pipes with a torch is a leading cause of house fires during cold snaps, and it can ignite framing inside a wall hours later. Use a hair dryer moved steadily along the pipe, an electric heating pad wrapped around it, towels soaked in hot water and re-soaked as they cool, or a space heater set a few feet back. If any water has pooled, cut power to that circuit at the breaker first.

Work from the faucet end back toward the ice

Start at the point closest to the open faucet and move backward as flow returns. Heating the middle of a frozen section traps melt water between two plugs of ice with nowhere to expand, which is how pipes split during a thaw.

Reach a pipe inside a wall

Turn the house heat up and open the cabinet or closet nearest that wall. An infrared lamp aimed at the wall surface from a safe distance works slowly but works. Opening the drywall is the last resort and the point at which most people should stop.

When to call a licensed plumber. Call if you cannot find or reach the frozen section, if it sits inside a finished wall or under a slab, or if the pipe is bulging or already leaking.

If water appears as the ice releases. Close the main shutoff immediately and leave it closed until the pipe is repaired.