To thaw a frozen pipe safely, first locate the main shut-off, then open the tap the pipe feeds and warm the frozen section gently, starting nearest the tap and working back toward the ice. Use a hair dryer, heating pad, warm towels or a space heater warming the room, never an open flame. If the pipe is split, shut off the main at once.
- Order matters: find the main shut-off, open the tap, then warm from the tap end back so meltwater and pressure have an exit.
- Gentle, attended heat works: Toronto and Calgary both list a hair dryer, heating pad, electric heater or warm towels; Toronto says thawing can take one to six hours.
- Never use a torch or any open flame, and do not use kerosene or propane heaters or charcoal stoves indoors; Winnipeg also warns against boiling water.
- A heat gun is not a safe default: it can scorch framing, melt plastic pipe and overheat a joint. If one is used at all, keep it on low and moving on exposed metal only.
- Once water flows, keep a thin trickle running and fix the cause before the next cold night.
01 /What should I do before I start thawing?
Before any heat goes on the pipe, get ready for the chance that it has already split. A frozen section can hold a crack shut with ice, and the leak starts the moment it thaws. Three minutes of preparation turns a potential flood into a wet towel.
- Find the main shut-off and test it
It is usually where the water service comes through the basement floor or foundation wall, next to the meter. Make sure it turns. If it is stuck, find out now, not with water spraying.
- Open the tap the frozen line feeds
Open both hot and cold if you are unsure which side froze. The open tap lets water and steam escape as the ice melts and shows you the moment flow returns. Toronto's advice is to open a basement tap, preferably the cold laundry tap, as well.
- Clear the area
Move stored items away from the pipe, lay towels or a tray under it, and keep cords and heaters off wet floors. Water and electricity should not meet.
- Find the frozen section
Trace the line from the dead fixture back to its coldest point. The frozen pipe signs guide shows how.
02 /Which way should I thaw the pipe?
Thaw from the open tap back toward the ice. Warming the section closest to the tap first gives melted water, and any steam from a hot spot, an easy path out through the open faucet. If you start at the far side of the ice, the melt forms a pocket behind the plug with no exit, which is the same trapped-water condition that splits pipes in the first place. The why frozen pipes burst guide explains that pressure pocket.
Keep the heat moving along the pipe rather than parked on one spot. You are trying to warm the metal and the ice slowly and evenly. A trickle from the tap is the first sign of success; keep warming until the flow is normal, then keep going a little further along the line, because a second plug may be waiting further back.
03 /Which thawing methods are safe?
The safe methods add modest heat, stay attended and keep flame away from the house. The City of Toronto lists an electric heating pad, a hair dryer, a space heater or a warm towel, and warns never to leave electrical devices unattended. The City of Calgary lists a hair dryer, heating pad, electrical heater, hot water bottles or hot towels. EPCOR in Edmonton suggests a hair dryer, space heater or heat lamp on narrow pipes, kept away from water and flammable materials.
| Method | Good for | Watch out for | Verdict |
|---|---|---|---|
| Hair dryer | Exposed pipe under a sink or in a basement | Keep it dry and moving; use a GFCI outlet near water | Safe first choice |
| Warm towels or hot water bottles | Short exposed sections, plastic pipe | Slow; rewarm often | Safe, gentle |
| Electric heating pad | A short exposed section | Never unattended; keep dry | Safe if watched |
| Space heater warming the room or cabinet | Pipes in a wall or cabinet you cannot reach | Keep a metre from anything that burns; never unattended | Safe if watched |
| Heat lamp aimed at a wall or pipe | Lines in exterior walls | Hot bulb; keep well back from combustibles | Use with care |
| Existing heat cable on the pipe | Pipes already fitted with cable | Check it is working and certified; do not add cable to ice | Fine if already installed |
| Heat gun | Exposed metal only, as a last resort | Can scorch wood, melt plastic pipe and overheat joints | Avoid; low and moving if used |
| Boiling water poured on the pipe | Nothing | Sudden temperature change; Winnipeg warns it can burst pipes | Do not use |
| Torch or any open flame | Nothing | House fires and steam pockets | Never |
| Kerosene, propane or charcoal heaters indoors | Nothing | Fire and carbon monoxide | Never |
04 /Is a heat gun safe for thawing pipes?
Treat a heat gun as a tool to avoid. A hair dryer delivers warm air; a heat gun delivers air hot enough to strip paint, and it can char the framing behind a pipe, ignite paper facing on insulation or dust in a cavity, melt PEX, CPVC or ABS, soften a solder joint and create a local hot spot that turns water to steam. Those risks are why this site does not recommend one for general thawing.
If a heat gun is the only tool available for an exposed copper line, use its lowest setting, keep the nozzle moving and well back from the pipe, shield nearby wood with a sheet of metal, never point it into a wall cavity, and never use it on plastic pipe or fittings. Stay with it, and have a fire extinguisher nearby. When the pipe is inside a finished wall, the safer path is warming the room and the wall, or opening an access hole, not blowing hot air at hidden framing.
05 /How do I thaw a pipe inside a wall or ceiling?
Warm the space around it rather than trying to reach the pipe. Turn up the heat in that room, open any cabinet doors below the fixture, and aim a space heater or heat lamp at the wall from a safe distance, staying with it the whole time. Warm air reaching the wall surface slowly drives heat into the cavity. It can take hours, and it may not work in a deep cold snap or behind thick insulation.
If gentle heat does not bring the water back within a few hours, the options are to open a small access hole in the drywall so the pipe can be warmed directly and inspected for a split, or to call a plumber. Opening the wall also lets you see whether the pipe sits against the sheathing, which is often the reason it froze. Once it is exposed, the where pipes freeze guide will help you decide whether to move it, seal the cavity or add insulation.
06 /How long does it take to thaw a frozen pipe?
Usually between one and several hours for an exposed or lightly buried section. The City of Toronto says that depending on the outside temperature and the extent of freezing, thawing could take between one and six hours. Short, exposed lines with a hair dryer can clear in well under an hour; a pipe inside an insulated exterior wall warmed from the room side can take much longer.
Frozen pipes also thaw on their own when the weather warms or the heat reaches them, but waiting has two costs: no water in the meantime, and a thaw that happens when nobody is watching. If the line split, an unattended thaw is how a small crack becomes a flooded basement. Controlled thawing, with the tap open and someone standing by, is the safer choice.
07 /What should I do after the water flows again?
- Keep the tap running at a thin trickle and inspect the whole thawed section for drips, bulges or dampness.
- Check the meter's leak indicator with every fixture off, to catch a split hidden inside a wall.
- Leave a thin trickle running from that tap until the cold snap ends. Winnipeg's guidance after a City thaw is a flow that fills a one-cup (250 ml) measure in about 15 seconds.
- Open cabinet doors, seal the draft you found and insulate the section before the next cold night.
- Plan the lasting fix: rerouting, sealing the cavity or heat cable. The prevention cost page has planning ranges.
If the service line or meter is frozen rather than a branch line, many utilities have their own thawing service and rules; see frozen water service lines and meters. If you cannot find or thaw the frozen section, request help through this site. If a pipe did burst, the next steps are on BurstPipe.ca.
FAQQuestions people ask
Should I turn off the main water when thawing a frozen pipe?
Keep it on but know exactly where it is and that it turns, so water can flow through the tap as the ice clears. If you see a crack, a weeping bulge or any leak, close it immediately.
Which end of a frozen pipe should I warm first?
The end nearest the open tap. Working back from the tap gives meltwater and steam an escape route, instead of trapping them behind the ice.
Can I use a hair dryer on a frozen pipe?
Yes, on an exposed pipe, kept moving and away from standing water, ideally plugged into a GFCI outlet. Stay with it. For underground service lines, follow your utility's instructions instead.
Is it safe to pour hot water on a frozen pipe?
Warm, wet towels are fine. Pouring boiling water directly on a pipe is not recommended; the City of Winnipeg warns it can burst pipes, and it soaks the area around electrical equipment.
Will frozen pipes thaw on their own?
Usually, once the air around them warms, but you lose control of the moment it happens. If the pipe split, the leak will start whenever it thaws, possibly overnight or while you are out.
Can I thaw PEX or plastic pipe the same way?
Use the gentle methods only: warm towels, a hair dryer on a low setting or warming the room. Never use a heat gun or flame on plastic pipe; high heat can soften or damage it.
When should I call a plumber for a frozen pipe?
When you cannot find the frozen section, it is inside a finished wall or ceiling, gentle heat has not worked after a few hours, the service line or meter is frozen, or the pipe is split.