Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.
Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.
Summary
Demand for this page arrives on a forecast, which is the worst possible moment to start reading. So it is written in the order the cold arrives: find the shut-off valve first, prepare the house second, get through the cold snap third, and deal with a pipe that has already frozen last. The order is deliberate. The advice everyone repeats — leave a tap dripping — is the last measure on the list, not the first, and it does nothing for a pipe in a draughty crawl space that nobody has ever insulated.
One instruction on this page is absolute and it is the reason the page exists. Never put an open flame near a frozen pipe. Seattle Public Utilities explains why: a blowtorch can make the water inside a frozen pipe boil and cause the pipe to explode, and every open flame in a house is a fire risk and a carbon monoxide risk on top of that. The CDC says the same thing more briefly — if your pipes do freeze, do not thaw them with a torch. This page will also tell you where its knowledge stops: no source read for it publishes an outside temperature that triggers any of this, and the sources disagree about how warm to leave an empty house, so both figures are printed with the authority that published each one.
Safety
DO NOT USE AN OPEN FLAME ON A FROZEN WATER PIPE.
Seattle Public Utilities says that a blowtorch can make the water in the pipe boil. The pipe can then explode. An open flame in a house is also a fire risk and a carbon monoxide risk.
Necessary equipment
| Item | Note |
|---|---|
| Flashlight | A crawl space and a basement are dark. |
| Caulk gun | Use the caulk gun on a crack near a water pipe. |
| Labels | Attach a label to the main shut-off valve. |
| Electric hair dryer | Use the hair dryer on a frozen pipe. |
| Cloth | Put the cloth in warm water before you apply it to a pipe. |
| Container | The container holds the water from the tap that drips. |
| Pipe sleeve material | The pipe sleeve must be the correct size for the pipe. |
| Exterior caulk material | Use a caulk that is applicable to the outside of a building. |
| Foam block or wood panel material | The block must close the foundation vent fully. |
Find the main shut-off valve
Estimated 10 min to 20 min
- Find the main shut-off valve for the water supply to the house.5mReport a problem with step 1, Find the main shut-off valve
- Denver Water says that the valve is usually in the basement or the crawl space.
- Denver Water says that the valve is usually on a wall that faces the street.
- Attach a label to the main shut-off valve.2mReport a problem with step 2, Find the main shut-off valve
- The label must show that this valve stops all the water in the house.
- Tell each adult in the house where the main shut-off valve is.3mReport a problem with step 3, Find the main shut-off valve
- Denver Water says that each person in the house must know how to stop the water.
- The National Weather Service in New York gives the same instruction.
Find the pipes that can freeze
Estimated 18 min to 33 min
- Examine each water pipe in an unheated space that you can touch from the floor.10mReport a problem with step 1, Find the pipes that can freeze
- DC Water says that such a pipe is often in a kitchen cabinet, an attic or a garage.
- DC Water also names a basement and a crawl space.
- The National Weather Service says that a pipe on an exterior wall has the highest risk.
- Examine the outside walls near each water pipe for a crack or a hole.5mReport a problem with step 2, Find the pipes that can freeze
- Cold air can move through a crack to the space around the pipe.
- Make a record of each water pipe that has no insulation.3mReport a problem with step 3, Find the pipes that can freeze
- Write the position of each pipe in the record.
Prepare the house before the cold weather
Estimated 48 min to 2 hr 22 min
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
- Seal each crack and each hole near a water pipe with caulk.15mReport a problem with step 1, Prepare the house before the cold weather
- The National Weather Service in New York gives this instruction for a wall and for a foundation.
- Sealed cracks stop the entry of cold air near the pipe.
- Install a pipe sleeve on each water pipe that has no insulation.20mReport a problem with step 2, Prepare the house before the cold weather
- DC Water says that you can buy a pipe sleeve at a store for building supplies.
- Obey the installation instructions from the manufacturer of the pipe sleeve.
- Seattle Public Utilities gives the same instruction about the manufacturer.
OPEN EACH FOUNDATION VENT AGAIN IN THE SPRING.
Seattle Public Utilities says that a vent that stays closed can cause dry rot.
- Close each foundation vent that is near a water pipe.10mReport a problem with step 3, Prepare the house before the cold weather
- Seattle Public Utilities says that a pipe in a draft from an open foundation vent has the highest risk.
- A cut piece of wood or a foam block can close the vent.
- Remove each hose from each outdoor tap.3mReport a problem with step 4, Prepare the house before the cold weather
- Water that stays in a hose becomes ice.
- Seattle Public Utilities also tells you to close the valve for the outdoor tap and to drain the line.
Steps during the cold weather
Estimated 8 min
Source: Home Preparedness Tips for Prolonged Frigid Cold (Public Information Statement) · tier 1 · accessed 2026-08-12
Source: Tips to prevent (and thaw) frozen water pipes in your home · tier 1 · accessed 2026-08-12
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
DO NOT USE A STOVE, AN OVEN OR A GRILL TO HEAT THE HOUSE.
These appliances can release carbon monoxide into the rooms. Carbon monoxide can kill you.
- Set the heating system to keep the house warm during the day and the night.2mReport a problem with step 1, Steps during the cold weather
- The National Weather Service in New York says to leave the heat set to at least 55 degrees.
- Denver Water says to keep the thermostat above 65 degrees if you leave for several days.
- The two figures do not agree. The specifications on this page name both sources.
- Open the cabinet door below each sink that is on an outside wall.2mReport a problem with step 2, Steps during the cold weather
- The Centers for Disease Control and Prevention gives this instruction for a kitchen sink and a bathroom sink.
- Warm air from the room can then move around the pipes.
- Close the door of an attached garage.1mReport a problem with step 3, Steps during the cold weather
- Denver Water says that a water pipe is sometimes in this unheated space.
- Open one cold tap to a slow drip.2mReport a problem with step 4, Steps during the cold weather
- Seattle Public Utilities says to select the tap that is farthest from your front door.
- Denver Water says to select the tap that is farthest from the point where the water enters the house.
- The Centers for Disease Control and Prevention says to leave all the taps at a slow drip.
- The sources do not agree about the number of taps. The specifications on this page give both instructions.
- Put a container below the tap that drips.1mReport a problem with step 5, Steps during the cold weather
- Denver Water says that you can then use this water in the house.
If no water comes from a tap
Estimated 50 min to 2 hr 20 min
Source: Safety Guidelines: During & After a Winter Storm · tier 1 · accessed 2026-08-12
DO NOT USE AN ELECTRICAL DEVICE IF THERE IS WATER ON THE FLOOR.
An electric shock can injure you or kill you. Speak to a licensed plumber instead.
KEEP THE TAP OPEN BEFORE YOU APPLY HEAT TO A FROZEN PIPE.
A closed tap holds the water between the tap and the ice. The pipe can then break.
- If no water comes from a tap, keep that tap open.<1mReport a problem with step 1, If no water comes from a tap
- Seattle Public Utilities says that a trickle from a tap is also a sign of ice in a pipe.
- Seattle Public Utilities says that water flow through the pipe melts more of the ice.
- Find the part of the pipe that has ice in it.10mReport a problem with step 2, If no water comes from a tap
- Seattle Public Utilities names a pipe against an exterior wall as a usual position.
- Seattle Public Utilities also names the position where the water supply enters through the foundation.
PUT EACH HEAT SOURCE AT A DISTANCE FROM MATERIAL THAT CAN BURN.
DC Water says to keep all sources of heat away from flammable materials. A heat source near such material can start a fire.
APPLY HEAT TO A FROZEN PIPE SLOWLY.
Denver Water says that a pipe that becomes warm too quickly can break.
- Apply heat to that part of the pipe with a warm cloth or an electric hair dryer.20mReport a problem with step 3, If no water comes from a tap
- The Centers for Disease Control and Prevention says to apply warm air from an electric hair dryer slowly.
- Seattle Public Utilities also names a towel in hot water and an electric heating pad.
- Denver Water says that a hair dryer at the frozen part of the pipe is applicable.
- Continue to apply heat until the water flows again.15mReport a problem with step 4, If no water comes from a tap
- Speak to a licensed plumber if the water does not flow again.
- Do a check of the other taps in the house.4mReport a problem with step 5, If no water comes from a tap
- Seattle Public Utilities says that more than one pipe can freeze.
If a pipe breaks
Estimated 6 min
- If a pipe breaks, close the main shut-off valve immediately.1mReport a problem with step 1, If a pipe breaks
- Seattle Public Utilities gives this instruction to stop the flood.
- Speak to a licensed plumber.5mReport a problem with step 2, If a pipe breaks
- Seattle Public Utilities says to repair or to replace the damaged pipe as soon as possible.
Terminology
This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.
- water pipe
- Also called: water line, supply line, water supply line, plumbing, the pipes in the wall, pipework
- main shut-off valve
- Also called: main water valve, main water shutoff, water shut off valve, stopcock, stop tap, the valve that turns the water off, house shut off
- pipe sleeve
- Also called: pipe insulation, pipe lagging, foam pipe wrap, foam tube for pipes, pipe wrap, pipe cover
- tap
- Also called: faucet, spigot, sink tap, kitchen faucet, bathroom faucet
- foundation vent
- Also called: crawl space vent, crawlspace vent, air brick, airbrick, the vent low down on the outside wall
- frozen pipe
- Also called: pipe froze, pipes are frozen, no water coming out of the faucet, frozen water line, frozen pipe what to do
When to use a professional
Stop if you cannot find the main shut-off valve. Speak to a licensed plumber before the cold weather starts. Without that valve you cannot stop the water from a broken pipe.
Stop if a water pipe is in an attic or below a floor. Speak to a licensed plumber. Speak to a licensed plumber also about a pipe that you cannot reach from floor level. This page covers only the pipes that you can reach safely from the floor.
Stop if you cannot find the part of the pipe that has ice in it. Seattle Public Utilities says to speak to a licensed plumber. Speak to a licensed plumber also if you cannot reach that part of the pipe. Speak to a licensed plumber if the water does not flow again.
Stop if a pipe breaks, or if water comes from a pipe or from a wall. Close the main shut-off valve. Speak to a licensed plumber immediately.
This page gives no procedure for an electric heating cable on a water pipe. Speak to an electrician about a heating cable, and obey the installation instructions from the manufacturer.
Speak to your water utility about the correct temperature for an empty house in your area. The sources on this page do not agree about that figure.
Common questions
Should I drip my faucets in cold weather, or is that an old wives' tale?
It is real advice from water utilities and from the National Weather Service, but it is the last measure on the list rather than the first. The National Weather Service in New York explains the mechanism: a dripping tap keeps unheated pipes from freezing, and keeping it open relieves the pressure that builds between the faucet and an ice blockage. Where the sources part company is how many taps. The CDC says to leave all water taps slightly open so they drip continuously; Seattle Public Utilities says to allow one indoor faucet to slowly drip cold water and to pick the one farthest from your front door; Denver Water says to crack the faucet farthest from where the water enters the house. We print all three rather than pick one, because they are three utilities writing for three climates. Denver Water adds a good detail — put a bucket under it and use the water for something.
How cold does it have to get before I need to do any of this?
We cannot tell you, and that is the honest answer rather than a coy one. Not one of the sources read for this page publishes an outside temperature that triggers these precautions. Seattle Public Utilities says "when it drops below freezing"; DC Water and the CDC say "in severe cold weather" and "very cold or freezing temperatures"; the National Weather Service statement behind much of this page was written for a specific forecast, not as a rule. The number you would want depends on wind, on how long the cold lasts, on where your pipes run and on how well the house is sealed, and no single figure covers that. Your own water utility publishes advice for your climate, and the forecast is the trigger.
What should I leave the heat at if I go away in winter?
The sources disagree, so both figures are on this page with the name of whoever published each. The National Weather Service in New York says not to turn the heat down too much if you are going away and to leave it set to at least 55 degrees; Seattle Public Utilities says to set the thermostat no lower than 55 degrees day or night, even if you are away; DC Water says to leave the temperature set above 55 degrees. Denver Water, writing for a colder and higher place, says to keep the thermostat set above 65 degrees when leaving your house or business for several days. We are not going to average 55 and 65 into 60. Ask the utility that serves you.
I turned the tap on and got a trickle. Is the pipe frozen?
Seattle Public Utilities says to suspect exactly that: if you turn on a faucet and only a trickle comes out, suspect a frozen pipe. Leave that tap open — as the ice melts, the water moving through the pipe helps melt the rest. Then look for the frozen section. The likely places are pipes running against exterior walls and the point where the water service enters the house through the foundation. Check the other taps in the house too, because if one pipe froze, others may have.
Can I use a blowtorch or a heat gun on a frozen pipe?
No, and this is the one instruction on the page with no exceptions. Seattle Public Utilities is explicit: do not use a blowtorch, kerosene or propane heater, charcoal stove, or other open flame device, because a blowtorch can make water in a frozen pipe boil and cause the pipe to explode, and all open flames in homes present a serious fire danger as well as a severe risk of exposure to lethal carbon monoxide. The National Weather Service says simply "Never use an open flame." DC Water says never to attempt it using an open flame of any kind. The CDC says if your pipes do freeze, do not thaw them with a torch. Denver Water puts it shortest: a hair dryer pointed at the frozen area of the pipe is appropriate, a blow torch is not.
Why does this page not tell me to put a space heater next to the pipe?
The National Weather Service does list a space heater among the ways to warm a frozen pipe, alongside a heating pad, an electric hair dryer and hot water on a cloth. We left it out of the steps on purpose. A page cannot supervise a heater left running in a crawl space, and the consequences of getting that wrong are not the same as the consequences of a slow thaw. For scale, CPSC estimates that portable heaters are involved in about 1,700 fires per year, resulting in about 80 deaths and 160 injuries annually. If you do use one, CPSC says to keep flammable materials at least three feet away and to plug it directly into a wall outlet rather than a power strip — and DC Water's rule covers every method: keep all sources of heat away from flammable materials.
What about heat tape or an electric heating cable on the pipe?
There is no procedure for it on this page. A heating cable is a permanently powered electrical product fitted to a water pipe, its correct length and thermostat depend on the installation, and getting it wrong has a fire history that is the reason the CPSC has written about heat tapes at all. That is an electrician's job and a manufacturer-instructions job, not a checklist job. If you already have one fitted, the manufacturer's instructions are the authority on inspecting it before winter.
The pipe already burst. What do I do first?
Close the main shut-off valve, which is why finding and labelling it is the first section of this page rather than an afterthought. Seattle Public Utilities gives the same order: if a water pipe breaks, immediately close the main shut-off valve to stop flooding, then call a plumber to repair or replace the damaged section as soon as possible. Do not use electrical devices where there is standing water. If you cannot close the valve, your water utility is the next call — Seattle's, for instance, staffs a line around the clock and will send a crew to shut the water off at the meter.
Does insulating a pipe stop it freezing?
It slows heat loss; it does not add heat. A pipe sleeve buys time in a cold snap and it is worth fitting, but on its own it will not save a pipe in a long freeze in an unheated space with a draught blowing on it. That is why the sources pair it with sealing the cracks, closing the foundation vents and keeping the house warm. DC Water suggests a pipe sleeve for water pipes that are not insulated and says building supply stores carry them; both DC Water and Seattle Public Utilities tell you to follow the manufacturer's installation instructions, and neither publishes a thickness, so neither do we.
Related procedures
- How do I insulate the hot water pipes at my water heater
- How to find your main water shut off valve and check that it actually works
- How do I safely heat my house when the power goes out?
- How to winterize an outdoor faucet so it does not burst in winter
- How to get the house ready for a storm and a power outage
- How to fix an outside tap that drips or won't shut off by replacing the washer and the packing inside the stem
- How to tell if you have a hidden water leak using your water meter
- How to start up a garden irrigation or sprinkler system in spring
Sources
Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.
- Tier 1Home Preparedness Tips for Prolonged Frigid Cold (Public Information Statement)
- Tier 1Essential Tasks After it Warms Up
- Tier 1Frozen Pipes in Winter Weather
- Tier 1Protect your Pipes from the Cold
- Tier 1Tips to prevent (and thaw) frozen water pipes in your home
- Tier 1Safety Guidelines: During & After a Winter Storm
- Tier 1Millions in Path of Winter Storms this Week; CPSC Issues Safety Tips to Help Families Prevent Carbon Monoxide Poisoning and Fires
Revision history
Current version 1 · updated 2026-08-12 · next review due 2027-08-12
- v1 · 2026-08-12First draft. Every source was fetched and read in this session on 2026-08-12. Five new sources are staged in data/sources-additions-prevent-frozen-pipes-in-a-cold-snap.json: the NWS New York public information statement (dated 2017-12-26), the NWS national 'Essential Tasks After it Warms Up' page (undated), Seattle Public Utilities (undated), DC Water (undated) and Denver Water (dated 2025-01-14). Two already-registered sources were re-read today through WebFetch because cdc.gov and cpsc.gov both returned HTTP 403 to a direct GET from this session: cdc-winter-storm-safety (page dated Feb. 7, 2024) and cpsc-winter-storm-co-and-fire-safety-tips (released 2022-02-01). Only the three dated sources carry a verified specification, because config.json thresholds treats an undated source as archaic. Two thermostat figures are published side by side with a conflict_note rather than reconciled: 55 °F from the National Weather Service in New York, 65 °F from Denver Water. The number of taps to leave dripping is published as a second, unverified disagreement between the CDC and Seattle Public Utilities. No trigger temperature is published at all, because no source read publishes one. Space heaters and electric heating cables are deliberately absent from the steps and are explained in the FAQ and the professional boundary. Ready.gov, the CPSC winter-storms safety guide, the CPSC 1990 heat-tape release and the Austin Water cold weather page are recorded under rejected with their HTTP status. Two figures quoted from the CPSC release on 2026-08-12 and used in the FAQ, because they are not in that source's registered notes: 'Make sure to keep flammable materials at least three feet away.' and 'CPSC estimates that portable heaters are involved in about 1,700 fires per year, resulting in about 80 deaths and 160 injuries annually.' Neither is published as a specification; the space-heater clearance figure is deliberately not a specifications entry because this page carries no step that uses a space heater.
Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.
Comments and corrections
Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.
Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.