Frozen Pipes, Prevention and Safe Thawing

Why Frozen Pipes Burst

Water expands by about 9 percent when it freezes. You might think the ice itself splits the pipe, but the burst often happens somewhere else. As an ice plug forms, it traps water between the ice and a closed faucet. More ice keeps forming and pushes that trapped water, and pressure builds until the weakest spot gives way.

That is why the crack may not be where the ice is, and why a small drip helps. An open faucet gives the trapped water somewhere to go, so pressure cannot build.

A burst often goes unnoticed until the pipe thaws. While frozen, the ice holds the water back. When it warms up, water pours out of the split. Many people discover a burst pipe the day after a cold snap, sometimes after they have left for work.

Copper and galvanized pipe tend to split. PEX plastic pipe can stretch and often survives a freeze better, but its fittings, valves and fixtures can still crack. No pipe material makes a house freeze proof.

Which Pipes Are at Risk

Pipes freeze where cold air reaches them and heat does not. Walk your home with a flashlight and look for these spots.

• Hose bibs and outdoor faucets
• Sprinkler lines and irrigation backflow devices
• Pipes in unheated garages, crawlspaces, basements and attics
• Pipes in outside walls, especially under kitchen and bathroom sinks
• Pipes near foundation vents, dryer vents or gaps where cold air leaks in
• Pipes in cabinets on outside walls, where the closed door keeps room heat out
• Water lines to an ice maker that run along an outside wall

Many plumbers treat about 20 degrees Fahrenheit outdoors as the point where pipes in unheated or poorly insulated spaces are in real danger. Pipes in very drafty spots can freeze at milder temperatures, especially with wind. A long cold snap is more dangerous than a single cold night.

If you remember a pipe that froze before, it will likely freeze again in the same conditions. Fix that spot first, with insulation, air sealing or a heat cable.

Prevention Before Winter

Most freeze damage is preventable with a few hours of work in the fall.

• Outdoor faucets. Disconnect garden hoses. A hose left attached traps water, even in a frost free faucet. Close any indoor shutoff that feeds an outdoor faucet, then open the outdoor faucet to drain it. Add an insulated cover.
• Irrigation. Shut off and drain sprinkler systems as the maker or installer directs, and insulate or drain the backflow device.
• Insulation. Put foam sleeves on pipes in garages, crawlspaces, attics and basements. Seal gaps where cold air blows on pipes.
• Heat cable. For pipes that still freeze, use a heat cable listed for pipe use and install it exactly as the instructions say. Self regulating types are safer than old constant wattage cables.
• Garage. Keep the garage door closed if water lines run through it.
• Crawlspace. Close foundation vents during deep cold if your home’s design allows it, and repair broken vent covers.

Insulation slows heat loss but does not add heat. A pipe in an unheated space with no heat source can still freeze during a long cold spell, so combine insulation with a heat source or the cold night habits below.

Cold Night Habits

When a hard freeze is in the forecast, a few simple moves protect the pipes you cannot easily reach.

• Keep the heat on. Set the thermostat to the same temperature day and night. Do not let it drop below 55 degrees Fahrenheit, even when you are away.
• Open cabinet doors under sinks on outside walls so room heat reaches the pipes. Move cleaning products out of reach of children and pets.
• Let faucets drip. On the coldest nights, let a faucet served by at-risk pipes drip slowly. For a single handle faucet, set it in the middle so both hot and cold lines move.
• Open interior doors so heat spreads to rooms with exposed plumbing.
• Check in the morning. Turn on each faucet. Low flow or none at all is an early warning.

The water cost of a slow drip is small compared with a burst pipe. If you lose power or heat during a freeze, drain the plumbing if you expect the outage to last and the house to drop below freezing. Never bring a grill or fuel burning heater indoors to keep warm, because they produce deadly carbon monoxide.

How to Tell a Pipe Is Frozen

The most common sign is a faucet that gives only a trickle or no water at all during cold weather, while other faucets work. Other signs include frost on an exposed pipe, a pipe that bulges, a strange odor from a drain and toilets that do not refill.

First, figure out whether the whole house is out or just one fixture.

If you see water, turn off the main shutoff right away and skip ahead to the burst pipe steps. If the whole house is dry, check with neighbors and your water utility before you start thawing. In some areas, the meter or the service line can freeze, and that may be the utility’s job.

Thawing a Frozen Pipe Safely

If you can see and reach the frozen section, you can usually thaw it yourself. Work slowly. Never use a torch or open flame. It can overheat the pipe, melt solder or plastic, and start a fire inside the wall.

• Open the faucet the pipe feeds. As ice melts, the water needs somewhere to go, and running water helps melt the rest.
• Start at the faucet end and work back toward the frozen spot, so melting water can flow out rather than getting trapped.
• Use a hair dryer, a heating pad, a space heater set a safe distance away, or towels soaked in hot water and wrapped around the pipe.
• Keep applying heat until full water pressure returns.
• Check every other faucet in the house. If one pipe froze, others may have too.

For pipes inside a wall, raise the heat in the room, open the cabinet and aim a heater toward the wall from a safe distance. If that does not work within a few hours, call a plumber. A pro may use tools that thaw pipes safely without opening the wall.

Watch closely as the pipe thaws. If water starts to spray or drip, shut the main off at once.

If a Pipe Has Burst

A split pipe can release several gallons a minute. Move fast.

1. Shut off the main water valve. Then open the lowest faucet in the house to drain the lines.
2. Cut the power to any area where water is reaching outlets, lights or appliances, but only if you can reach the panel without standing in water.
3. If the water heater is off, turn off its power or gas to protect the tank.
4. Take photos of the break and the damage before cleanup.
5. Remove water with towels, mops and a wet dry vacuum, and get fans and a dehumidifier running.
6. Call a plumber to repair the pipe and your insurer to report the loss.

Water that sits in drywall, insulation and carpet pad can grow mold within 24 to 48 hours, so drying fast matters. If water soaked more than one room, ran for more than a few hours or got into ceilings below, a water damage restoration company with moisture meters and drying equipment is usually worth it.

Many homeowners policies cover sudden bursts from freezing, but some exclude freeze damage when a home was left without heat or not drained while vacant. Read your policy before winter.

Step by Step

1. Find the Main Shutoff

   Before thawing anything, find the main water valve and make sure it turns. If the pipe has split, you will need it fast.

2. Open the Faucet

   Open the faucet the frozen pipe feeds, both hot and cold on a single handle faucet. This relieves pressure and lets melting water flow out.

3. Locate the Ice

   Trace the pipe back from the faucet and look for frost, bulges or the coldest section, often where the pipe runs along an outside wall or through an unheated space.

4. Apply Gentle Heat

   Warm the pipe from the faucet end toward the ice with a hair dryer, heating pad or hot wet towels. Keep heaters a safe distance away and never use a flame.

5. Wait for Full Pressure

   Keep heating until water runs at full pressure. Then leave the faucet dripping for a while to keep water moving.

6. Check for Leaks

   Look along the pipe and at nearby walls, ceilings and floors for drips as water pressure returns. Shut the main off at once if you find one.

7. Check Every Faucet

   Run each faucet in the house. If one pipe froze, others in similar spots may have too.

8. Fix the Cause

   Insulate the pipe, seal cold air leaks or add a listed heat cable so the same pipe does not freeze again.

Mistakes That Make It Worse

• Using a propane torch to thaw a pipe. It can melt joints and start a fire hidden inside the wall.
• Thawing a pipe without knowing where the main shutoff is. A split pipe floods fast once the ice melts.
• Leaving a hose attached to a frost free faucet. It traps water and the faucet can still split inside the wall.
• Turning the heat way down during a trip in winter. It is one of the most common causes of freeze bursts.

Where You Live Matters