How to Prevent Frozen Pipes: The Night-Before-a-Freeze Checklist and the 20°F Rule

Frozen pipes rarely happen because people don't know what to do. They happen because the cold night arrives, everyone goes to bed, and nobody remembered to open the cabinet under the sink or leave a tap dripping.

The fixes are cheap and quick. The hard part is doing them on the right night, and doing the autumn jobs before the first hard frost rather than after it.

Below: the temperature to watch for, the jobs to do in autumn, a five-minute checklist for the night before a freeze, what to do if you're going away, and what to do if a pipe freezes or bursts anyway.

Why a frozen pipe is such an expensive problem

Water expands as it freezes. According to the American Red Cross, that expansion can break metal or plastic pipes alike, however strong they are.

Oddly, the pipe usually doesn't split where the ice is. Research summarised by South Carolina Farm Bureau Insurance explains that once ice blocks a pipe, continued freezing pushes up the water pressure between the ice and the closed tap, and that's where the pipe fails. It's also why a dripping tap helps: an open tap gives that pressure somewhere to go.

The damage shows up when the ice melts and water pours out. State Farm reports more than 20,000 frozen-pipe and winter water damage claims from 2024 through June 2025, with paid losses over $628 million and an average claim payment above $30,000. It also notes that a small crack in a pipe can release more than 250 gallons of water a day.

What temperature do pipes freeze at?

Water freezes at 32°F (0°C), but the pipes in a house don't usually freeze the moment it drops below that outside.

The figure most insurers use is 20°F (about -7°C). It comes from research by the Building Research Council at the University of Illinois: in field tests, uninsulated pipes in an unheated attic began to freeze when the outside temperature fell to 20°F or below. A survey of 71 plumbers in southern US states found the same thing: burst pipes started appearing when temperatures dropped into the teens (SC Farm Bureau Insurance).

Two important caveats:

• Pipes can freeze above 20°F. If cold air blows directly across a pipe, through a crack in an outside wall or a gap where a cable comes in, it can freeze at higher temperatures. Wind makes it worse.
• Homes in warmer places are often more at risk, not less. In southern states, pipes are more likely to run through attics, crawl spaces and outside walls, and people are less used to preparing for the one or two hard freezes a year.

So treat a forecast of 20°F / -7°C or lower as your signal to act, and act sooner if you know your house has a cold spot or the forecast is windy.

Which pipes freeze first

The Red Cross lists the most common problem pipes:

• Pipes exposed to severe cold: outdoor hose taps (hose bibs), swimming pool supply lines and sprinkler lines.
• Supply pipes in unheated areas such as basements, crawl spaces, attics, garages and kitchen cabinets.
• Pipes that run along outside walls with little or no insulation.

Take five minutes to walk round and find yours. If you can't see a pipe, look for where your water supply comes into the house, and check the sink cabinets that sit against outside walls.

The autumn jobs: do these before the first hard frost

These are one-off jobs for the season. October is a good time for most of Canada and the northern US. Do them a little later in milder areas, but always before the first forecast freeze.

1. Shut off and drain the outdoor taps. Close the indoor valve that supplies each outdoor tap. Unscrew the garden hose, then open the outdoor tap to let the water drain out. The Red Cross says to leave the outdoor tap open, so any water left in the pipe has room to expand without breaking it. Peel Region in Ontario gives the same advice: do it in the fall, before the first frost.
2. Drain sprinkler and pool supply lines, following the manufacturer's or installer's instructions. The Red Cross warns not to put antifreeze in them unless you're told to, because it's harmful to people, pets and wildlife.
3. Insulate exposed pipes in the garage, crawl space, attic and under sinks on outside walls. Foam pipe sleeves are cheap. UL-listed heat tape or heat cable is an option for problem spots. In Canada, Peel Region suggests looking for CSA or UL certification.
4. Seal the draughts. Look for cracks and gaps near pipes, especially where cables or lines come through an outside wall.
5. Find your main water shut-off valve, and make sure it turns. If a pipe bursts, this is the first thing you'll need, and that's a bad moment to be looking for it. British Columbia's emergency management team puts it simply: "righty tighty."

The night-before-a-freeze checklist

When the forecast shows 20°F (-7°C) or colder, do this in the evening, before bed:

• Drip a tap. Let cold water drip from the tap fed by your most exposed pipes. The Red Cross says that running water through the pipe, even at a trickle, helps stop it freezing.
• Open the cabinet doors under kitchen and bathroom sinks so warm air from the room can reach the pipes. Move cleaning products and other chemicals out of reach of children and pets first.
• Close the garage door if any water pipes run through the garage.
• Don't turn the heating down at night. The Red Cross recommends keeping the thermostat at the same temperature day and night during a cold snap. Your heating bill will go up a little; a burst pipe costs far more.
• Know where the main shut-off is, and make sure the way to it isn't blocked.

The next morning:

• Turn on each tap. If only a trickle comes out, the Red Cross says to suspect a frozen pipe (see below).
• Keep dripping on each night the cold continues. Stop once it warms up again.

If you're going away this winter

An empty house is the worst place for a pipe to freeze, because nobody notices until the ceiling comes down.

• Leave the heating on. The Red Cross and State Farm both say to keep it no lower than 55°F (about 13°C). Canadian guidance is similar: British Columbia says no lower than 12°C, and Peel Region says no lower than 15°C (60°F).
• Ask someone to check the house. Peel Region suggests a daily check while you're away for a long time, to make sure the heating is still on and there are no leaks.
• For a long trip, think about shutting off the water. Peel Region suggests turning off the main valve and draining the pipes from a tap on the lowest floor. Be careful if you have a home fire sprinkler system: State Farm points out that shutting off the water also shuts off the sprinklers.

If a pipe has frozen

Signs: you turn on a tap and only a trickle comes out. Frozen sections are most likely along outside walls or where the water supply comes into the house through the foundation.

The Red Cross advice:

1. Keep the tap open. As the ice melts, water flowing through will help melt the rest.
2. Warm the pipe with an electric heating pad, a hair dryer, a portable space heater kept away from anything flammable, or towels soaked in hot water.
3. Never use an open flame. No blowtorch, kerosene or propane heater, or charcoal stove.
4. Keep going until full water pressure is back. Then check every other tap in the house, because if one pipe froze, others may have too.
5. Call a licensed plumber if you can't find the frozen section, can't reach it, or can't thaw it.

State Farm adds two safety points: don't use electrical appliances near standing water, and when using a hair dryer, start near the tap and work back towards the frozen section.

If a pipe has burst

1. Turn off the main water valve straight away, and leave the taps open (State Farm).
2. Keep away from electrics near any standing water.
3. Call a plumber, then your insurer. Take photos of the damage before you start clearing up.

A simple frozen-pipe reminder plan

Every step above takes a few minutes. They go wrong because of timing: the autumn jobs get put off until it's already freezing, and the night-before jobs get forgotten at 11pm. A handful of reminders fixes that:

When	Reminder
Mid-October, or a couple of weeks before your usual first frost	"Outdoor taps: close the inside valves, take the hoses off, open the taps to drain. Check the pipe insulation in the garage."
The same weekend	"Find the main water shut-off and check it turns."
Evening of any night forecast at 20°F / -7°C or below	"Freeze tonight: drip the kitchen tap, open the sink cabinets, close the garage, leave the heating where it is."
The next morning	"Check every tap has full pressure. Keep dripping if it's still freezing tonight."
The day before a winter trip	"Heating at 55°F / 13°C minimum. Ask a neighbour to check the house."

If you're in a mild area that only gets one or two hard freezes a year, those freeze nights are exactly the ones nobody is ready for. Setting the reminder the moment you see the forecast is what makes the difference.

For the rest of the year's house jobs, see our seasonal home maintenance checklist.

How ReminderIt can help

A note on the fridge doesn't help at 10pm when you're already in bed. ReminderIt rings your phone at the time you choose and reads your reminder out in a natural voice: "Hard freeze tonight. Drip the kitchen tap and open the cabinet under the sink." If you miss the call, the reminder comes through on WhatsApp too.

ReminderIt doesn't watch the weather for you, so set the reminder when you see the forecast. That takes seconds: send a WhatsApp message such as "Call me tonight at 9pm to drip the taps and open the sink cabinets, and again at 7am tomorrow to check the water pressure." You can also set reminders on the website. While you're at it, set one for mid-October so the outdoor taps get done in time.

If you look after an older parent's home, a freeze night is a good time to give them a call as well. You can set a reminder that rings their phone with the checklist. They confirm their number once with a short verification call, so nobody gets calls they didn't agree to. Our guide to cold-snap check-ins for an older relative covers the rest of what to ask about.

There's a 7-day free trial with 7 reminder calls. (It's 3 calls if your number is in a country where calls cost more, such as the UK; the US and Canada aren't among them.) After that it's one plan: US$7 a month, or ₹299 a month in India.

The short answer

Most house pipes start to freeze when it's 20°F (about -7°C) or colder outside, sooner if cold wind reaches them. Before the first frost, shut off and drain your outdoor taps and insulate exposed pipes. On any night forecast at 20°F or below, drip a cold tap fed by exposed pipes, open the sink cabinets and keep the heating steady. If you're away, keep the heat at 55°F (13°C) or higher. If a pipe freezes, keep the tap open and warm it gently, never with a flame. If one bursts, turn off the main water valve.

Sources: American Red Cross, Preventing & thawing frozen pipes; South Carolina Farm Bureau Insurance, How pipes freeze and burst (University of Illinois Building Research Council findings); State Farm, Frozen pipes? Not so nice!; Government of British Columbia, Simple ways to prevent your pipes from freezing this winter; Region of Peel, Preventing frozen pipes.