How to Prevent and Fix Frozen Pipes

Why Pipes Freeze

When the air surrounding water pipes drops below freezing, the water in the pipes can freeze. At the very least, the ice can block the flow of water to faucets; worse, the pipe can burst, creating a mess, causing water damage and requiring pipe replacement.

It's easy to see how pipes are prone to freezing if they're in an unheated area such as a garage, attic or crawl space, or are in exterior walls and ceilings. Understanding why pipes inside the house freeze — especially in a building that has seen its fair share of winters — is trickier. Pipes in the exterior wall of a 50-year-old house might freeze after you add insulation from the inside of the house, because less heat escapes through the wall to warm the pipe. If a kitchen remodel includes installing a closed cabinet under the sink, those pipes might freeze because they're cut off from the warm, circulating air. Moving a heat source further from pipes during a remodeling project also could lead to a freeze.

Frozen pipes can crack or burst when they begin thawing, because the thawed water is trapped between the ice block and a closed faucet, creating pressure on the pipes.

Some types of pipes are more likely to burst than others. Copper pipes, for example, tend to swell, but the piping may not split or burst on the first freeze. Some types of plastic supply pipe withstand freezing conditions better than copper. The most common pipes, galvanized steel, tend to burst more often.

How to Prevent Freezing

Prevention is the best solution for frozen pipes. You have several options, some of which you can combine:

Keep the thermostat above 60°F so the air near pipes is warm.
If pipes run through or under your attached garage, keep the garage door closed.
Insulate exposed pipes with foam tubing — it's slit on one side so it's easy to slip over the pipe. Or install electric heating cables, which typically wrap around the pipe and are secured with tape.
When frigid temps are predicted during the night or while you're away during the day, open the faucet a little to let the water drip slowly. Moving water is less likely to freeze, and if it does freeze, the open faucet keeps pressure from building. Also open the cabinet door under sinks on outer walls to let warm air get to the pipes.
When remodeling, reroute the pipes to a warm location.

Exterior pipes to garden faucets have a shut-off valve inside of older homes. In late autumn, shut off the inside valve and open the outside valve to allow any water to drain. Some interior valves have auxiliary bleed valves to drain water that is downstream of the winter shut-off valve. Homes built since the 1970s have frost-proof exterior faucets — when you turn off the water, the shut-off valve inside the house closes. These frost-proof valves don’t require a permanent shutoff in the winter.

What to Do If a Pipe Freezes

Open faucets a little and, if possible, shut off the water supply to the frozen pipes to decrease pressure. Drips from a close faucet can be a sign that pressure is building.
Wrap exposed pipes in towels soaked in hot water.
Use a blow dryer or heat lamp to slowly warm them. You can use this technique for exposed pipes and those inside a wall. If warming a wall with a heat lamp, be extremely careful to not heat the wall enough to combust.