Frozen Pipes: How to Thaw Them Safely

Frozen pipes usually announce themselves on the first bitter morning of the year, when you turn on a faucet and get a thin trickle or nothing at all. The good news is that most frozen lines can be thawed safely with a hair dryer and some patience, as long as you find the problem before the pipe splits.

TL;DR

A faucet that only trickles in freezing weather most likely has a frozen supply line, often along an exterior wall or where the water line enters the house.
Open the affected faucet, then warm the pipe gently with a hair dryer, heating pad, or hot wet towels, working from the faucet end back toward the ice.
Never use a torch, propane or kerosene heater, charcoal stove, or any open flame.
If a pipe has burst, shut off the main water valve first, then call a plumber and your insurance company.
Prevent repeats by keeping the heat at 55°F or higher, dripping faucets on exposed lines, opening sink cabinets, and insulating vulnerable pipes.

Why Pipes Freeze
Symptoms and Likely Causes
How to Thaw Frozen Pipes Step by Step
What Not to Do
When to Call a Professional
How to Prevent It
FAQ

Why Pipes Freeze

Water takes up more room as it turns to ice. Inside a closed pipe, that expansion builds pressure, and the American Red Cross notes it can crack metal and plastic pipes alike, no matter how sturdy they are.

Freezes almost always start in pipes that get less heat than the rest of the house. Here are the situations that set one up.

Pipes in Unheated Spaces

Supply lines that run through crawl spaces, attics, garages, and unheated basements sit in air that can drop well below freezing. Kitchen and bathroom sink cabinets on outside walls count too, because the closed cabinet door keeps room heat away from the pipes.

Pipes Along Exterior Walls

A pipe inside a thinly insulated exterior wall can freeze even when the room feels warm.

Outdoor Faucets, Hoses, and Sprinkler Lines

Hose bibs, irrigation lines, and pool supply lines take the brunt of the cold. A garden hose left attached traps water in the faucet, so it can’t drain. The Insurance Institute for Business & Home Safety (IBHS) points out that homes built before 2010 often lack frost-proof outdoor faucets, which makes them more vulnerable.

Low or Fluctuating Indoor Heat

Turning the thermostat way down at night or while you travel lets wall cavities and cabinets cool off fast. IBHS also notes that homes in southern regions tend to run into more plumbing trouble during extreme cold.

Symptoms and Likely Causes

Use this table to match what you’re seeing to the most likely problem.

Symptom	Likely cause	DIY or pro?
One faucet trickles or runs dry; others work	Frozen branch line to that fixture, often under a sink on an outside wall	DIY if you can reach the pipe
Hot side works, cold side doesn’t (or the reverse)	Only one supply line frozen	DIY
No water anywhere in the house	Freeze near the main entry point, or a utility-side problem	Check with neighbors and your water utility; call a plumber if it’s your line
Outdoor faucet won’t run	Frozen hose bib or hose left attached	DIY; leave it alone until it thaws if you can’t reach the indoor valve
Water dripping or spraying, wet drywall, or a puddle	Burst or cracked pipe	Shut off main water now, then call a pro
Pipe is inside a finished wall or ceiling and won’t thaw	Inaccessible frozen section	Pro

If water comes back but pressure stays weak at just one shower after a cold spell, a partial freeze may still be lingering. Once everything is fully thawed, see our guide to fixing low water pressure in a shower to rule out clogged aerators and showerheads.

How to Thaw Frozen Pipes Step by Step

Tools you may need: a hair dryer, an electric heating pad, old towels and a bucket of hot water, a flashlight, a portable space heater with automatic shutoff, and a bucket or towels for drips.

Safety first: Keep every electric appliance out of standing water, and don’t stand in water while you use one. Plug corded tools into a GFCI-protected outlet when one is available. If you see water spraying or pooling, shut off the main valve (see Step 1) before you do anything else.

Step 1: Check for a Burst and Locate Your Main Shutoff

Before you add heat, look along the pipe for cracks, bulges, or water. If the pipe has already split, thawing it will release water, so close the main shutoff valve first. It’s usually close to where the water line enters the house, such as in a basement, crawl space, or utility room.

Even if nothing looks broken, find that valve now. University of Illinois Extension stresses that knowing how to stop the water quickly is what limits damage if a crack shows up mid-thaw.

Step 2: Find the Frozen Section

Start at the faucet that isn’t working and trace its supply line back. The Red Cross suggests checking pipes against exterior walls and where the water service comes through the foundation first.

If several fixtures are dead, focus on the main line near where it enters the house.

Step 3: Open the Faucet

Turn on the faucet the frozen pipe feeds, both hot and cold if you aren’t sure which side is frozen. An open faucet relieves pressure, and moving water helps melt the remaining ice as it starts to flow.

Step 4: Apply Gentle Heat, Starting Near the Faucet

Begin warming the pipe at the faucet end and work slowly back toward the frozen spot. That way, meltwater always has an open path out instead of being trapped behind the ice. Good heat sources include:

An electric hair dryer, moved back and forth along the pipe
An electric heating pad wrapped around the pipe
Towels soaked in hot water and wrapped around the pipe, swapped out as they cool
A portable space heater aimed at the area, kept well away from anything flammable

The CDC recommends thawing pipes slowly with warm air from a hair dryer. If you’re also running a space heater, plug them into different circuits. If your circuit breaker keeps tripping, that’s a sign you’ve overloaded one circuit.

Step 5: Keep Going Until Full Pressure Returns

A trickle means the ice is opening up, but don’t stop yet. Keep heating until the faucet runs at normal pressure, which tells you the line is fully clear.

If you spot a drip or spray as the ice melts, shut off the main valve right away.

Step 6: Check Every Other Faucet

One frozen pipe often means others are frozen too. Run each sink, tub, and shower briefly.

Step 7: Watch for Leaks Over the Next Few Days

University of Missouri Extension warns that pipes frozen for several hours may have cracked, and a small split might not leak much at first. Look under sinks, along ceilings below bathrooms, and at basement walls for damp spots or stains.

If a faucet keeps dripping after the thaw even when it’s fully closed, the cold may have stressed its washer or cartridge. Our guide on how to fix a leaky faucet walks through that repair.

If a Pipe Has Burst

Close the main water shutoff valve.
If water is near outlets, cords, or appliances, stay out of it. University of Illinois Extension warns of shock risk around standing water, so call your electric utility or an electrician if power and water have met.
Call a plumber and your insurance agent, and take photos of the damage.
Use bottled water or a neighbor’s water until the pipe is repaired, as the CDC suggests.

Move fast. University of Illinois Extension notes that a crack just 1/8 inch wide can let out up to 250 gallons of water in a day.

What Not to Do

Don’t use any open flame. That means no propane torch, blowtorch, kerosene or propane heater, charcoal stove, or candle. University of Missouri Extension explains that a torch can make the water inside boil and the pipe burst, and open flame creates fire and carbon monoxide risk.
Don’t bring grills or camp stoves indoors. The CDC warns that fumes from charcoal and gas grills, camp stoves, and generators are deadly inside homes, basements, and garages.
Don’t close the faucet while thawing. Meltwater and pressure need somewhere to go.
Don’t use electric tools around standing water. If the area is wet, deal with the water first.
Don’t run a space heater unattended or on an extension cord. The CDC advises keeping it at least 3 feet from furniture, drapes, and bedding.

When to Call a Professional

The Red Cross advises calling a licensed plumber when you can’t find the frozen spot, can’t reach it, or can’t get it to thaw. Call right away for any of these warning signs:

A pipe is cracked, bulging, leaking, or spraying
The frozen section is inside a finished wall, ceiling, or under a slab
The whole house has no water and the main line itself seems frozen
Water has reached electrical outlets, fixtures, or appliances
Your main shutoff valve is stuck or won’t close fully

If water from a burst line soaked a garage or basement where your water heater sits, have the plumber check it too. Our guide to a leaking water heater can help you tell whether a puddle is coming from the tank or the pipes around it.

None of the sources consulted for this guide list typical repair costs, so get a quote before work begins. Contact your insurer early, since University of Illinois Extension recommends calling your agent along with the plumber.

How to Prevent It

Before Cold Weather Arrives

Disconnect and store garden hoses.
Close the indoor valve that feeds each outdoor faucet, then open the outdoor faucet to drain it and leave it open.
Cover outdoor faucets with an insulated foam cover.
Drain sprinkler and pool supply lines following the manufacturer’s or installer’s directions. Skip antifreeze unless they specifically call for it.
Insulate exposed pipes in attics, crawl spaces, garages, and under sinks with foam pipe sleeves.
Seal air leaks where pipes, vents, and wiring pass through exterior walls.
Check attic insulation and cover vented crawl space openings temporarily for the winter.

For pipes that freeze year after year, UL-listed heat tape or heat cable is an option. Install it exactly as the manufacturer directs, and seal pipe sleeve seams with waterproof tape so they stay snug. If you plug heat cable into a GFCI outlet and it trips and stays off, see our guide on what to do when a GFCI outlet won’t reset.

During a Cold Snap

Let a thin stream of cold water drip from faucets served by exposed pipes. Even a trickle keeps water moving.
Open kitchen and bathroom sink cabinets on outside walls, and move cleaning products out of children’s reach.
Keep the thermostat at the same setting day and night, no lower than 55°F.
Keep the garage door closed if water lines run through the garage.

Holding a steady temperature may raise your heating bill a little, but the Red Cross notes it can head off a far more expensive burst pipe. If you’re on a septic system, UGA Extension cautions against leaving taps dripping for long stretches, because the extra water can overload the system. Rely more on heat, insulation, and open cabinets instead.

When You Travel

Leave the heat on at 55°F or higher. University of Illinois Extension suggests having someone check daily that the heat is still running, or shutting off and draining the water system before you go.

FAQ

How do I know if my pipes are frozen?

The classic sign is a faucet that gives only a trickle, or nothing, during freezing weather. If only one fixture is affected, trace its supply line back toward the nearest outside wall.

Will frozen pipes thaw on their own?

They may once temperatures rise, but waiting is risky. The longer a pipe stays frozen, the more likely it is to crack, and you won’t know until it thaws and leaks.

At what temperature do pipes freeze?

There isn’t one number, because it depends on how exposed and insulated the pipe is and how long the cold lasts. Pipes in unheated spaces and outside walls freeze first. Keeping your home at 55°F or higher and following the cold-snap steps above greatly lowers the odds.

Should I let all my faucets drip at night?

Focus on faucets fed by pipes in exterior walls, cabinets, or unheated spaces. IBHS suggests letting faucets drip during extreme cold, and a thin trickle is enough. If you’re on a septic system, limit dripping and lean on heat and insulation.

Can I use a heat gun to thaw a frozen pipe?

The safer choices are a hair dryer, heating pad, or hot wet towels, all of which give slow, even warmth. None of the safety agencies cited here recommend a heat gun, and the goal is gentle warmth, so stick with the tools they list. Never use a propane torch or any open flame.

Frozen Pipes: How to Thaw Them Safely and Stop Them From Freezing