What to Do When a Pipe Freezes, Before It Bursts

If a faucet that always runs is dripping or dry in freezing weather, a pipe upstream is probably frozen. Ice is a plug, and the water behind it has nowhere to go. This is the best moment you will get: the pipe may not have split yet, nothing is wet, and a few safe minutes with a hair dryer can save a flooded house. The steps below are in the order that keeps people and property safe.

How to tell a pipe is frozen

• One faucet or fixture gives no water, or only a trickle, while others work.
• Frost on a visible pipe, or a pipe that feels much colder than its neighbors.
• A bulge in a visible pipe, a crack, or any moisture on it. These mean it may already have split.
• Odd smells from a drain, which can mean a frozen drain line instead of a supply line.

If every fixture is dry, the problem may be the main line, the meter or the utility, and the ice may be in the line outside the house where you cannot reach it.

The first three steps

1. Open the faucet, hot and cold, fully. As ice melts, the water and pressure need a way out, and an open faucet shows you the moment flow returns.
2. Find the main shutoff and make sure you can reach it. Triple-I’s guidance is to know where your pipes are and how to shut off the water, and that if pipes freeze, speed is critical. IBHS makes the same point about knowing the main shutoff. The shutoff guide shows how.
3. Check for leaks you can already see. Look at the pipe, the wall and the ceiling below for any water. If you see any, close the main now.

How to thaw a pipe safely

The aim is gentle, steady warmth, starting at the end closest to the open faucet and working back toward the frozen section. That order lets melted water escape instead of trapping pressure between the ice and a closed point.

• A hair dryer on a low or medium setting, moved along the pipe. Keep it dry and keep yourself out of any water.
• An electric heating pad wrapped around the pipe.
• Warm, damp towels wrapped around the pipe, re-warmed as they cool.
• Raising the temperature of the room or opening cabinet doors under the sink so warmer air reaches the pipe.

Keep going until full flow returns. Then leave the faucet running lightly for a while and check the pipe along its length for drips or damp.

What never to use

A quick triage

Common thawing mistakes

• Closing the faucet too soon. The faucet has to stay open so water and pressure can escape as the ice melts, and so you can see flow return.
• Heating the middle first. Starting in the middle can trap water between ice plugs and build pressure. Start near the faucet.
• Walking away. A thawing pipe can split as the ice melts. Stay close, at least for the first stretch, and know where the main shutoff is.
• Assuming one frozen pipe means one problem. Lines in the same wall, attic run or garage share the same exposure. Check them.
• Using more heat than the pipe needs. Gentle and steady beats fast and hot.

If the frozen pipe is the main line or the water heater supply, or if you cannot find where the ice is, a plumber is the right call. A house with no water in freezing weather and no visible frozen pipe usually has ice somewhere you cannot see.

After the water comes back

A split pipe can look fine while it is full of ice and start to leak as it melts, so the watchful period is after the thaw. Look at the pipe and the surrounding wall, ceilings below, cabinet bases and the floor at the lowest point. Then run a meter check. EPA’s WaterSense guidance says to check your water meter before and after a two-hour period when no water is being used, and that if the meter changes at all, you probably have a leak. After a freeze, that is a quick way to catch one you cannot see.

Also check the other lines in the same wall or attic run, since they had the same exposure. If you find water, the first hour plan applies, and the post on leaks after a thaw explains the timing in detail.

Drain lines, condensate lines and sprinklers

Not every freeze problem is a supply line.

• Frozen drains. Slow draining, gurgling and a drain that stops are signs. A drain line that freezes can back up into a sink or tub. Warm the pipe as you would a supply line if you can reach it, and do not pour chemicals down a drain that may be blocked by ice.
• Furnace condensate lines. High-efficiency furnaces drain a small amount of water through a thin line. If it freezes, the furnace can shut down, which then puts the plumbing at risk. A technician can thaw and reroute it.
• Water heater lines. The cold supply and the relief valve discharge are both exposed in attics and garages. Check them for ice.
• Interior sprinklers. IBHS says plumbing and interior sprinklers may freeze in extreme cold, particularly during power outages. Do not thaw sprinkler lines yourself. Call the installer.
• Irrigation. Backflow assemblies and exposed risers freeze. Close the supply inside the house, then drain the system.

Pipe material changes the risk

Rigid pipes such as copper and CPVC split when ice expands inside them. Flexible plastic pipe such as PEX tolerates more expansion and is less likely to split along its length, but fittings, connections and any rigid sections can still fail. Which material you have depends on the age and the builder, and it does not remove the need for insulation and a shutoff you can reach. If you do not know, a plumber can tell you in a few minutes and can point out the lines most exposed to cold.

For preparation before the next cold snap, see how to protect pipes before a Dallas freeze, based on the DFW weather record and IBHS guidance. The burst pipe checklist is a printable version of the steps if the pipe does fail.

Read about frozen and burst pipe cleanup →

This article is general information from the Dallas Flood Guard editorial team. It is not medical, legal, engineering or insurance advice. Sources are linked above. See the editorial policy for how posts are researched and corrected.