How to Thaw Frozen Pipes
Updated February 25, 2026
Safely thaw a frozen water pipe using a heat gun, hair dryer, or heat tape -- without bursting the pipe or starting a fire.
Overview
A frozen pipe is an emergency waiting to happen. Water expands 9% when it freezes. That expansion creates pressure between the ice blockage and the closed faucet -- up to 25,000 PSI in extreme cases. The pipe does not burst where the ice is. It bursts at the weakest point between the ice and the faucet, often in a completely different section of pipe. The goal is to thaw the ice slowly from the faucet side back toward the frozen section, allowing melting water to drain as it thaws. Never thaw from the middle -- trapped pressure has nowhere to escape and the pipe bursts.
What You'll Need
Safety First
- Never use an open flame (propane torch, blowtorch, lighter) to thaw pipes. Fire risk is extreme -- insulation, wood framing, and wall materials are inches away from the pipe. Torches also cause uneven heating that can boil water inside the pipe and split it.
- If the pipe has already burst (you see water damage, hear running water in a wall, or find a split pipe), turn off the main water supply immediately before thawing. Thawing a burst pipe with the water on floods the house.
- Frozen pipes in walls, ceilings, and concrete slabs are difficult to reach. If you cannot access the frozen section, call a plumber -- they have specialized equipment (electric pipe thawing machines) that heat the pipe from the inside.
Step-by-Step Instructions
- Identify the Frozen Section
Turn on the faucet served by the suspected pipe. No water or just a trickle? Confirmed frozen. Follow the pipe from the faucet back toward the water source. Feel the pipe with your hand (wear gloves in cold areas). The frozen section feels ice-cold and may have visible frost on the exterior. Common freeze locations: exterior walls, unheated crawlspaces, attics, garages, and under kitchen sinks on exterior walls.
Tip: If multiple faucets are not working, the freeze may be on a main supply line that feeds all of them. Trace back to the common point -- often where the main enters the house through a foundation wall. - Open the Faucet
Open the faucet that the frozen pipe feeds -- both hot and cold handles if it is a two-handle faucet. This gives melting water somewhere to go and relieves pressure in the pipe as the ice thaws. Running water, even a trickle, also helps melt the remaining ice from the inside. Keep the faucet open during the entire thawing process.
Tip: Open faucets on BOTH sides of the frozen section if possible. If the freeze is between a faucet and a branch tee, opening the faucet downstream of the freeze allows water to drain as it melts. - Apply Heat from the Faucet Side Back
Start at the faucet (or the nearest open end) and work backward toward the frozen section. This ensures melting water can drain toward the open faucet. Methods: Hair dryer (most common, safest): hold 6-12 inches from the pipe, move back and forth. Heat gun (faster, but be careful on PVC -- it melts at 140-160°F): keep moving, do not hold in one spot. Heat tape or heat cable: wrap around the pipe and plug in -- provides slow, even heating. Hot towels: soak towels in hot water, wrap around the pipe, replace as they cool. Space heater: place near the frozen section in an enclosed area (crawlspace, cabinet) to raise the ambient temperature.
Tip: A hair dryer is the safest and most available tool. It takes 20-45 minutes to thaw a typical frozen section but has zero fire risk and zero chance of overheating the pipe. Patience over speed. - Monitor for Leaks as Ice Thaws
As the ice melts, water starts flowing. Watch the entire visible pipe section for drips, sprays, or splits. A pipe that burst during freezing may not show damage until the ice thaws and water pressure returns to the cracked section. If you see a leak, turn off the main water supply immediately. Mark the leak location. The burst section needs repair or replacement before restoring water.
Tip: Sometimes the burst is inside a wall where you cannot see it. If you restore flow after thawing but hear running water inside a wall, or if you see water stains on a ceiling or wall surface, a pipe has burst behind the drywall. Main off, call a plumber. - Prevent Refreezing
After thawing, take immediate steps to prevent refreezing: leave the faucet dripping at a slow trickle (moving water freezes at a lower temperature). Open cabinet doors under sinks on exterior walls to let warm room air reach the pipes. Insulate the pipe with foam sleeves if it is accessible. For chronic freeze locations, install heat tape ($15-$30 per run) with a thermostat that activates automatically below 38°F.
Tip: A pencil-thin stream of water prevents freezing in most conditions. The water does not need to flow fast -- just enough to prevent standing water in the pipe from reaching 32°F. Cost: $5-$15/month in water, far less than a burst pipe repair.
Pro Tips
- Pipes freeze because they are exposed to air below 20°F for more than 6 hours. The most vulnerable locations: exterior walls without insulation, unheated crawlspaces, attics, garages, and where supply lines enter the house through the foundation.
- Heat tape (electric heat cable) is the permanent solution for pipes in chronic freeze zones. Self-regulating heat tape ($15-$30 per run) adjusts its output based on the pipe temperature -- no thermostat needed. It only draws power when the pipe is cold.
- If you are leaving the house during a cold snap, set the thermostat no lower than 55°F. Open cabinet doors on exterior walls. Leave a faucet dripping on the farthest fixture from the water heater.
- PEX pipe survives a single freeze event better than copper because it can expand slightly and return to shape. Copper is rigid and splits. Neither is freeze-proof -- both fail under repeated freeze-thaw cycles.
- Insurance covers burst pipe damage in most homeowner policies, but prevention is far better than a claim. A burst pipe in an unoccupied home can cause $10,000-$50,000+ in water damage before anyone notices.
When to Call a Pro
Call a plumber if the frozen pipe is inside a wall, ceiling, or concrete slab where you cannot access it (they have electric pipe thawing machines that heat from inside the pipe). Call immediately if the pipe has already burst (main off first, then plumber). Call if multiple pipes are frozen simultaneously (may indicate a failed furnace or a heat source problem that needs addressing before any pipes are thawed).
Frequently Asked Questions
When should I call a plumber to thaw frozen pipes?
Call a plumber if the frozen pipe is inside a wall, ceiling, or concrete slab where you cannot access it (they have electric pipe thawing machines that heat from inside the pipe). Call immediately if the pipe has already burst (main off first, then plumber). Call if multiple pipes are frozen simultaneously (may indicate a failed furnace or a heat source problem that needs addressing before any pipes are thawed).
What are some expert tips to thaw frozen pipes?
Pipes freeze because they are exposed to air below 20°F for more than 6 hours. The most vulnerable locations: exterior walls without insulation, unheated crawlspaces, attics, garages, and where supply lines enter the house through the foundation. Heat tape (electric heat cable) is the permanent solution for pipes in chronic freeze zones. Self-regulating heat tape ($15-$30 per run) adjusts its output based on the pipe temperature -- no thermostat needed. It only draws power when the pipe is cold. If you are leaving the house during a cold snap, set the thermostat no lower than 55°F. Open cabinet doors on exterior walls. Leave a faucet dripping on the farthest fixture from the water heater. PEX pipe survives a single freeze event better than copper because it can expand slightly and return to shape. Copper is rigid and splits. Neither is freeze-proof -- both fail under repeated freeze-thaw cycles. Insurance covers burst pipe damage in most homeowner policies, but prevention is far better than a claim. A burst pipe in an unoccupied home can cause $10,000-$50,000+ in water damage before anyone notices.
What tools do I need to thaw frozen pipes?
You will need: Hair dryer (safest heat source for thawing), Heat gun (faster but requires caution -- do not overheat PVC or CPVC), Heat tape or heat cable ($15-$30 per run, for permanent prevention), Foam pipe insulation ($0.50-$1.50/foot, for post-thaw protection), Towels (for hot-towel method and for catching drips from potential leaks).
When should I call a professional instead of doing this myself?
Call a plumber if the frozen pipe is inside a wall, ceiling, or concrete slab where you cannot access it (they have electric pipe thawing machines that heat from inside the pipe). Call immediately if the pipe has already burst (main off first, then plumber). Call if multiple pipes are frozen simultaneously (may indicate a failed furnace or a heat source problem that needs addressing before any pipes are thawed).
How difficult is this project?
This project is rated easy. Most homeowners with basic tools can complete it.
How long does this take?
Plan for approximately 30 - 90 minutes. First-timers may need extra time.
How much will this cost?
The estimated cost is $0 - $30. Costs vary by location and materials chosen.