How to Thaw Frozen Pipes Safely

Open the faucet that is not working. Nothing, or a thin trickle that dies within a few seconds, means an ice plug — a fixture that runs normally for a moment and then stops is usually a supply or pressure problem instead. Now open every other faucet in the house, hot and cold, and note which ones are dead. One dead fixture points at a single branch line; the whole house dead points at the main service line where it enters the foundation.

Before any heat goes on the pipe, know where the main shut-off is and confirm it turns. It is usually where the service line comes through the foundation wall, often near the water heater or meter, and it will be either a lever-handled ball valve or a round-handled gate valve. If a thawing pipe turns out to be split, you have seconds — not minutes — to stop hundreds of gallons from reaching your framing.

Follow the dead fixture's supply line back toward the water heater or main and look at the cold parts of the run: pipes against exterior walls, in an unheated crawl space, garage, attic, or along the rim joist. Run a bare hand slowly along the pipe — the frozen length reads noticeably colder and often carries a dull rime of frost or beads of condensation at its edges. An infrared thermometer makes this quick, showing a run of pipe sitting at or below freezing while the rest reads room temperature.

This is the step almost everyone skips, and it is the one that decides whether you get a small repair or a ruined ceiling. With a flashlight, look closely at the frozen section for a length of pipe swollen out of round, a hairline crack running lengthwise, or a soldered or crimped fitting that has visibly pushed apart. Copper usually splits along its length rather than at a joint; plastic tends to fail at the fitting. While the ice is still in place it is plugging its own hole — the leak only starts once you thaw it.

Open both the hot and cold handles on the affected fixture and leave them open for the entire thaw. This does two things: it gives meltwater and any trapped air somewhere to escape instead of building pressure behind the plug, and it gives you a live progress indicator. The first sign of success is usually a spitting dribble as water starts working past the ice.

Start heating at the point closest to the open faucet and work slowly back toward the middle of the frozen section. Direction matters: heating the middle first traps meltwater between two ice plugs with nowhere to go, which is exactly the pressure that splits pipes. Wrap an electric heating pad around the pipe, play a hair dryer slowly back and forth along it, or wrap it in towels soaked in hot tap water and re-soak them every five to ten minutes. A space heater aimed at the general area works for pipes you cannot wrap, just keep it well clear of anything that burns.

Expect a sputtering trickle first, then a surge as the plug lets go. Keep the heat on that section for another ten minutes after flow returns — the plug rarely melts all at once, and a remaining collar of ice will refreeze the moment you walk away. Let the faucet run for several minutes to flush out any rust or sediment the ice shook loose, and watch the water for a moment: it should run clear and at the same pressure as an unaffected fixture.

Go back to the list you made in step one and open each fixture again, hot and cold. Pipes that froze once are all sitting in the same cold air, so a second or third plug elsewhere in the house is common and easy to miss while you are focused on the first one. Do not forget outdoor spigots, a basement utility sink, a laundry hookup, and the line feeding an ice maker or humidifier.