The worst part of a cold snap isn’t the forecast — it’s the guessing. Do you need to drip the faucets tonight, or is that just wasting water? Is 28°F a problem, or only 15°F? And if you rent a third-floor apartment with pipes you can’t even see, what are you supposed to do about any of it?
Frozen pipes are one of the few home problems where a ten-minute job the night before can head off a five-figure repair. Yet most advice online is either vague (“keep your home warm!”) or written for someone with a basement, a garage, and a truckload of tools. Renters and small-space owners need something else: a clear trigger temperature for every action, fixes that don’t involve drilling into walls, and an honest line between what you can handle and what needs a licensed pro.
That’s this guide. Below: the temperature thresholds that actually matter, a band-by-band checklist from 40°F down to below zero, how to size pipe insulation for your climate, what a protective drip really costs on your water bill, and exactly what to do — and what to check first for your own safety — if a pipe bursts. Screenshot it or tape it inside a cabinet door. When the forecast drops, you’ll know what to do and what you can skip.
Quick Facts
| Detail | Figure |
|---|---|
| Water freezes at | 32°F / 0°C |
| Widely cited “temperature alert threshold” for uninsulated pipes in unheated spaces | 20°F / -6.7°C (attributed to Building Research Council research at the University of Illinois) |
| Temperature at which dripping stops being optional | 25°F and below (everything above that band is preparation, not protection) |
| Volume increase when water turns to ice | About 9% |
| Typical household supply pressure | 40–80 psi (a pressure-reducing valve is commonly required above 80 psi) |
| Recommended minimum thermostat setting for an unoccupied home in winter | 55°F / 13°C |
| Water released by a 1/8-inch crack in a supply pipe | More than 250 gallons per day (Insurance Institute for Business & Home Safety) |
| Water used by a one-drop-per-second drip | About 0.3 gallon per hour — roughly 4 gallons over a 12-hour night (3,000+ gallons if left running all year) |
| Cost of that overnight drip | About 2–12 cents, using combined water-and-sewer rates of roughly $5–$30 per 1,000 gallons across U.S. utilities |
| How to size pipe insulation | By the pipe’s outside diameter, not its nominal size — and by your area’s winter design low |
| Time to shut off the main after a burst | Under 60 seconds — after you’ve ruled out electrical, injury, and gas hazards |
Why Pipes Burst (It’s Not the Ice You Think)
Most people assume ice swells until it splits the pipe at the frozen spot. That’s only half right. Water does expand about 9% when it freezes, but the damage usually comes from hydraulic pressure.
Here’s the sequence. Ice forms first at the coldest point — typically where a pipe crosses an exterior wall, an unheated crawlspace, or a garage. That plug blocks the line. Water stays trapped between the ice and your closed faucet, and as the plug grows it shoves that trapped column of water against the closed valve with nowhere to go. Pressure spikes far above normal household supply pressure of 40–80 psi, and the pipe lets go — often several feet away from the ice, at a fitting, a solder joint, or a thin spot where little or no ice has formed.
Two practical takeaways:
- An open faucet relieves the pressure. That’s the whole logic behind dripping. Even if ice forms, an escape path dramatically lowers the odds of a burst.
- No pipe material is freeze-proof. Copper splits cleanly. CPVC turns brittle in the cold and cracks. PEX is generally the most forgiving because it can stretch, but its brass and plastic fittings can still fail. If someone told you “you have PEX, don’t worry,” read that as lower risk, not no risk.
The factor that matters as much as the low temperature is duration. A three-hour dip to 18°F right before sunrise is far less dangerous than 26 straight hours at 22°F. Pipes have thermal mass, and they’re buffered by framing, air pockets, and sometimes insulation. Cold has to soak in. So when you read the forecast, count the consecutive hours below freezing — not just the overnight low.
The Master Checklist by Temperature
How to Read These Bands
The bands below are cumulative preparation, not seven different freeze predictions. Pipes in a heated home do not freeze at 38°F. The top two bands exist because that’s the last comfortable moment to pull hoses, buy sleeves, and find your shutoff while the shelves are stocked and your hands still work outdoors.
The temperature where the pipe itself is genuinely at risk is the 20°F alert threshold for an uninsulated pipe in an unheated space. This checklist starts dripping one band early, at 25°F, so the trickle is already running before the pipe reaches that threshold. So the short version: above 25°F you are preparing; at 25°F and below you are protecting. The “Drip tonight?” column says so explicitly for every band.
Use the overnight low from your local forecast. If you’re in the South or the Pacific Northwest, where pipes are more often run through unheated attics and vented crawlspaces, act one band earlier than the table says — which means your dripping trigger becomes 32°F rather than 25°F.
| Overnight low | Risk level | Drip tonight? | What to do |
|---|---|---|---|
| 40°F+ / 4°C+ | Prep window | No — nothing is at risk | Disconnect and drain garden hoses. Find your main water shutoff and confirm it actually turns. Buy foam sleeves and faucet covers now, before the pre-storm rush empties the shelves. |
| 33–40°F / 1–4°C | Low — setup only | No. Water in the pipe is nowhere near freezing; this band is for installing things, not running water | Put covers on outdoor faucets. Insulate any pipe you can see and reach in a crawlspace, garage, or utility closet. Close crawlspace vents if yours have covers. Do this in daylight, before the first hard freeze arrives. |
| 25–32°F / -4–0°C | Moderate | Not yet — unless it will stay below freezing for 24+ hours, it’s windy, or your pipes run through an unheated attic or vented crawlspace. Then start the trickle described in the next band. | Keep the garage door shut. Hold the thermostat at 65°F or above, day and night, with no setback. At dusk, open the doors of every sink cabinet and vanity whose back wall is an exterior wall — usually the kitchen sink, plus bathrooms on an outside corner — and any laundry or utility closet door on an exterior wall. Leave them open all night and close them the next morning once the outdoor temperature is back above 32°F and rising. Move cleaners, medications, and sharps out of any open cabinet first if you have kids or pets. Shut off and drain irrigation lines and any outdoor shower. |
| 20–25°F / -7–-4°C | Alert | Yes. Start at dusk, leave it running until the outdoor temperature clears 32°F the next day | Everything above, plus an overnight trickle at your most exposed fixture — usually the faucet farthest from the water heater or the one on an outside wall. Leave interior doors open so heat circulates. |
| 10–20°F / -12–-7°C | High | Yes — every at-risk fixture, hot and cold sides | Trickle every fixture fed by pipes in exterior walls or unheated space. Thermostat at 68°F with no night setback. Energize any pipe heat cable. Check the temperature inside sink cabinets with an inexpensive thermometer. |
| 0–10°F / -18–-12°C | Severe | Yes — multiple fixtures, continuously | Steady trickle at multiple fixtures. Run water through every toilet, tub, and washer hookup at least once every 4–6 hours. Keep the path to the main shutoff clear. Text a neighbor if you’ll be out. |
| Below 0°F / -18°C | Extreme | Yes — and verify flow every 3–4 hours | All of the above, rechecked every 3–4 hours while you’re awake. If the house will sit empty more than a day, shut off the main and drain the system, or arrange a daily check. Watch for pressure drops — a weakening stream at one tap is the earliest sign of a forming ice plug. |
Wind Changes the Math
Wind doesn’t make the air colder, but it pulls heat off exposed surfaces much faster and drives cold air through every gap in your building envelope. A stiff 20–30 mph wind funneling through a quarter-inch gap at a rim joist, dryer vent, or crawlspace vent can leave a nearby pipe far colder than it would be on a still night at the same air temperature. On windy nights, move up one risk band — a windy 28°F night gets treated as a 22°F night, which means the trickle goes on — and pay extra attention to the windward side of the building.
Where Pipes Actually Freeze in Apartments and Small Homes
You can’t protect what you haven’t found. Spend 20 minutes mapping your risk zones once, and every future cold snap becomes a five-minute routine.
| Location | Relative risk | What to do about it |
|---|---|---|
| Outdoor hose bib with a hose still attached | Very high | Pull the hose. Add an insulated dome or sock cover. The highest-payoff three minutes in this article. |
| Vented crawlspace, uninsulated pipe | Very high | Foam sleeves on every reachable run, close the vents, seal obvious drafts. |
| Unheated attic runs (common in the South) | Very high | Insulate — but only if you can get there safely from fixed stairs. Otherwise hire a pro. Don’t climb into an attic on a ladder mid-emergency. |
| Attached garage with laundry or a water heater | High | Keep the door closed and insulate the pipes; a closed garage stays meaningfully warmer than outdoor air. |
| Kitchen sink on an exterior wall | High | Open the cabinet doors at dusk; trickle the tap on alert nights. |
| Bathroom on an exterior corner (two cold walls) | High | Open the vanity, leave the door open, trickle both taps. |
| Unheated utility or laundry closet with exterior access | High | Weatherstrip the door and add a draft stopper at the threshold. |
| Interior-wall pipes in a heated apartment | Low | Normally fine, as long as the heat stays on. |
| Units over a garage or on a slab-edge ground floor | Elevated | Floor cavities dump heat downward; open cabinets and trickle on high-risk nights. |
A useful trick: on a cold evening, set an inexpensive digital thermometer inside the sink cabinet and shut the doors. If it reads below 45°F, that pipe needs help. Open the doors, check again in an hour, and you’ll usually see a clear rise — proof that the simplest tactic on this list actually works.
The Prep Kit: What to Buy and Roughly What It Costs
These are ballpark U.S. retail ranges from recent big-box pricing. Costs move with region and season — and they spike right before a storm — so verify before you budget.
| Item | Typical size / spec | Ballpark cost | Renter-friendly? |
|---|---|---|---|
| Polyethylene foam pipe sleeve | 6 ft length, self-sealing slit | $2–$5 each | Yes — no fasteners needed |
| Fiberglass pipe wrap | 25 ft roll, 3 in. wide | $8–$15 | Yes (wear gloves and a mask) |
| Insulated faucet cover (dome or sock) | Fits standard hose bibs | $5–$12 | Yes |
| Self-regulating pipe heat cable | Sold in fixed lengths — 6, 12, 24, 50 ft | $30–$90 | Usually — plug-in models |
| Foil tape for insulation seams | 1.9 in. x 50 yd | $8–$14 | Yes |
| Rope caulk / removable seal | 90 ft coil | $5–$10 | Yes — peels off in spring |
| Door draft stopper | 36 in. under-door | $10–$25 | Yes |
| Wireless thermometer | Remote sensor, 1–3 zones | $15–$40 | Yes |
| Water leak sensor with freeze alert | Alert temperature varies by model — check the spec | $20–$50 | Yes |
| Smart automatic shutoff valve | Installs on the main line | Device plus plumber’s labor — get local quotes | Owners only |
Pipe Insulation: What Matters When You Buy It
Pipe insulation doesn’t make heat. It slows heat loss, which buys hours. That’s exactly what you need for a 12-hour cold snap — and nowhere near enough for a five-day deep freeze with no heat in the building. Be honest about which one you’re facing.
Thicker sleeve walls resist heat loss better, but published R-values vary between manufacturers, so check the datasheet on the package rather than trusting a rule of thumb.
Which Thickness for Your Climate
“Mild” and “cold” are useless words unless someone defines them, so here they are in numbers. Find the row that matches your typical January overnight low and how long your freezes usually last:
| Sleeve wall thickness | Climate it’s for — defined | Example regions | Notes |
|---|---|---|---|
| 3/8 in. | Mild: coldest nights rarely below 25°F, and freezes break by late morning (under about 12 hours below 32°F) | Gulf Coast, coastal and central California, low-desert Southwest, coastal Florida and the Deep South | Also fine anywhere for interior cabinet runs. Thin and flexible; easiest to snake into tight spots |
| 1/2 in. | Mixed: lows in the teens a few nights a year, freezes lasting roughly 12–36 hours | Mid-Atlantic, Tennessee Valley, western Oregon and Washington, north Texas and Oklahoma, southern Midwest | The default choice in most stores; the right pick for garages and utility closets in these areas |
| 3/4 in. | Cold: lows regularly 0–15°F, with multi-day stretches that never rise above freezing | Upper Midwest, Great Lakes, interior Northeast, Mountain West valleys | Crawlspaces and cold basements. Needs room to close around the pipe without gapping |
| 1 in. | Severe: sustained subzero periods, days at a time | Northern Plains, northern New England, interior Alaska, high-elevation Rockies | Long unheated runs. Confirm the R-value on the manufacturer’s spec sheet |
Not sure which row is yours? Two quick checks: look up your county’s average January low on any climate-normals page, or ask a local HVAC contractor for the 99% winter design temperature they use for load calculations — that single number is the industry’s answer to “how cold does it actually get here.” When you’re between two rows, buy the thicker one; the price difference is a dollar or two per length.
Sizing the Sleeve
Sizing goes by the pipe’s outside diameter, not the number stamped on the pipe. Measure or match against this:
| Nominal pipe size | Copper OD (ASTM B88) | Iron pipe size / PVC OD |
|---|---|---|
| 1/2 in. | 0.625 in. | 0.840 in. |
| 3/4 in. | 0.875 in. | 1.050 in. |
| 1 in. | 1.125 in. | 1.315 in. |
Three installation rules people skip:
- Leave no gaps. A two-inch bare stretch at an elbow becomes the new coldest point — and the new freeze location. Miter the sleeve ends at corners and tape every seam and joint.
- Block the cold, don’t block the heat. Where a pipe runs along an exterior wall inside a cabinet, the goal is to let warm room air reach the pipe while sealing out cold outside air. Sealing the wall penetration often matters more than wrapping the pipe.
- Don’t bury pipes under attic insulation. Pipes stay warm because your heated space keeps them warm. Putting insulation between the pipe and that heat is exactly backward.
Heat Cable: Useful, But Follow the Label
Electric pipe heating cable (often sold as heat tape) is the right answer for a pipe that can’t be kept warm any other way — a long crawlspace run, a well line, an exposed section under a manufactured home. It’s also a recurring cause of house fires when it’s misused, so treat the instructions as binding, not advisory.
| What to check | Why it matters |
|---|---|
| Wattage per foot and total length | Printed on the package. Buy a factory length that fits your run — you can’t trim cable to size. |
| Self-regulating vs. constant wattage | Self-regulating cable adjusts output with temperature and is more forgiving; constant-wattage cable is less tolerant of installation errors. |
| Thermostat | Built-in or inline; check the switching temperature on the spec sheet so you know when it energizes. |
| Pipe material rating | Cable intended for metal pipe can deform or melt plastic pipe. |
| Safety listing | Look for a nationally recognized listing mark (UL, ETL, or CSA) for pipe heating cable, and confirm it’s rated for residential use. |
| Circuit capacity | Add up the cable’s total wattage and make sure the outlet’s circuit can carry it alongside everything else plugged in. |
Safety rules, straight from the kind of language you’ll find in the instructions:
- Use a GFCI-protected outlet. Crawlspaces, garages, and exterior walls are damp environments, and ground-fault protection is the difference between a nuisance trip and a shock hazard. No GFCI where you need one? That’s a licensed electrician’s job — don’t open outlets or panels yourself.
- Never overlap the cable on itself, and don’t install it under foam pipe insulation unless the instructions specifically allow it. Overlapping traps heat and is a classic ignition source.
- Don’t cut, splice, or shorten it, and don’t run it through a wall.
- Inspect the cord and cable every fall for cracks, chew marks, and scorching, and replace anything questionable rather than gambling on another season.
- Plug it straight into a wall outlet. Skip extension cords. If a timer or strip is unavoidable, confirm its amp rating covers the load.
The same discipline applies to any small electric space heater you’re tempted to point at a cold pipe: plug it directly into a wall outlet, never into an extension cord or power strip, keep at least three feet of clearance from anything combustible, and don’t leave it running unattended in a crawlspace or closet. And never run a propane or kerosene heater in an enclosed crawlspace or indoors — carbon monoxide is odorless and it kills quietly.
Dripping Faucets: How Much, and What It Costs
Dripping works because it keeps water moving and gives ice-driven pressure somewhere to escape. Aim for a slow, steady trickle — visibly more than an occasional drop, well short of a running tap.
The cost depends entirely on your local rate, which varies more than most people realize. Water and sewer are usually billed together on volume, and the sewer charge is often larger than the water charge. Across U.S. utilities, combined rates commonly land somewhere between $5 and $30 per 1,000 gallons ($0.005–$0.03 per gallon). The table below spans that whole range, so find your own number and the estimates get exact.
| Flow | Roughly per hour | Over a 12-hour night | What it costs at $5–$30 per 1,000 gal |
|---|---|---|---|
| Slow drip, 1 drop per second | About 0.3 gallon | About 4 gallons | About 2–12 cents (that same drip left running year-round wastes 3,000+ gallons) |
| Slow, steady trickle | 1–3 gallons | 12–36 gallons | About 6 cents to $1.10 — a dime or two in most markets |
| Thin steady stream | 5+ gallons | 60+ gallons | $0.30–$1.80 — cheap, but scale it back; you’re overshooting |
| Burst pipe, 1/8-inch crack | — | — | More than 250 gallons per day, plus repairs and water damage |
Doing the Math on Your Own Bill
Pull your last water bill and find the volume rate. It’s printed either as dollars per 1,000 gallons or dollars per CCF (one CCF = 100 cubic feet = 748 gallons). Add the sewer volume charge, since almost every utility bills sewer on metered water use. Then: gallons used ÷ 1,000 × combined rate.
For scale, using recent published rate schedules, combined water-and-sewer costs run roughly $0.015 per gallon in New York City, roughly $0.008–$0.02 per gallon across much of Texas and the Southeast, and often $0.02–$0.04 per gallon in coastal California and the Seattle area, where supply and treatment costs are highest. So a 4-gallon overnight drip costs about 6 cents in New York, 3–8 cents in Houston, and 8–16 cents in the Bay Area. Even at the top of that range, a night of dripping through the coldest week of the year costs less than a cup of coffee. Rates change annually and tiered pricing can push heavy users higher, so treat these as orders of magnitude and check your own bill. On a private well you pay only the pump’s electricity — pennies either way — but you should still avoid running the pump all night if the tank is small.
Which faucet? Start with the fixture farthest from where water enters the home, plus anything on an exterior wall. If a single-handle mixing faucet serves that spot, park the handle in the middle so both hot and cold lines move. Hot lines are not immune — they freeze too, and they’re often less insulated than people assume.
One caution: don’t leave a trickle running into a sink with a sluggish drain in an unheated space, and never leave a plugged tub filling. If the drain ices up, you’ve traded a frozen pipe for a flood.
The Renter’s Playbook
If you rent, you have less control than an owner but more leverage than you think. Heat is almost always a landlord obligation under the implied warranty of habitability, and many cities and states set specific minimum indoor temperatures during heating season — New York City is one well-known example. Look up the rules where you live; the exact numbers differ, the principle rarely does.
Do this before the first hard freeze:
- Find your shutoff valves — under sinks, behind the toilet, and, if you can get to it, the main for your unit. Photograph them and note the locations in your phone.
- Email, don’t call. Report a cold room, a draft at a pipe, an uninsulated exterior line, or a heating system that can’t hold temperature — in writing, with the date and an actual thermometer reading, and a clear repair request. That paper trail is what protects your deposit if something bursts later.
- Ask two specific questions: where is the building’s main shutoff, and what’s the after-hours emergency number? Get both answers in writing.
- Stick to removable fixes. Foam sleeves, faucet covers, rope caulk, draft stoppers, and plug-in thermometers all come off without a trace. Don’t drill, don’t cut drywall, and don’t touch building mechanical equipment.
- Never shut the heat off completely when you travel. Many leases require a minimum setting, and 55°F is the standard floor. Leave a unit unheated and liability for burst pipes can land on you.
Leaving Town in Winter: The Away Checklist
- Set the thermostat to at least 55°F / 13°C — bump it to 60–62°F if you’ll be gone more than a week or the forecast looks severe.
- Open every under-sink cabinet and leave interior doors open. Since no one will be there to close them in the morning, leave them open for the whole trip.
- Close the washing machine supply valves. Burst washer hoses are one of the most common winter water losses.
- Ask a neighbor to check daily, and give them your plumber’s number and the shutoff location.
- Put a leak sensor with freeze alerting near the water heater and under the kitchen sink. Check each model’s alert temperature so you know how much warning you’re actually getting.
- For trips longer than a week in a cold climate, consider shutting off the main and draining the system: close the main, open the highest and lowest faucets, flush the toilets, and drain exterior lines. Don’t drain a water heater unless you know how to refill and restart it safely — with a gas unit, that means shutting off the gas first and following the manufacturer’s relighting procedure, or hiring a pro.
- Never put automotive antifreeze in household plumbing; it’s toxic. Non-toxic propylene glycol RV/marine antifreeze is for drain traps and winterizing, and only where the label says so.
If a Pipe Freezes: Safe Thawing
Warning signs: a faucet that dribbles instead of flows, no water at one fixture while others work fine, frost on a visible pipe, or a bulge or hairline split.
- Open the affected faucet — both hot and cold — and leave it open. This relieves pressure and gives meltwater a path out.
- Locate the main shutoff before you do anything else, so you can close it instantly if the pipe turns out to be cracked.
- Apply gentle, even heat, starting at the faucet end and working back toward the frozen section. Safe options: an electric heating pad wrapped around the pipe, towels soaked in hot water, or a hair dryer on low, kept constantly moving. Keep any electric device and its cord clear of standing water, use a GFCI-protected outlet, and unplug and cool tools before handling them.
- Warm the whole space rather than just the pipe when you can. An open cabinet plus a small heater aimed into the room — not at the pipe — works well and carries less risk.
- Be patient. A frozen section can take 30–60 minutes to clear, and flow returns as a sputter before it returns as a stream.
Never do these:
- No open flame. No propane torch, no blowtorch, no heat gun on high. Torch-thawing starts house fires every winter and can flash-boil water trapped inside the pipe.
- No kerosene or propane heaters in an enclosed crawlspace or anywhere indoors.
- Don’t keep forcing water through a pipe you can’t see or reach. If you can’t find the freeze, if it’s inside a wall, ceiling, or attic, or if you spot any crack or bulge, shut off the water and call a licensed plumber.
Skip the ladder heroics, too. Roof, attic-hatch, and gutter work on an icy day is a serious injury risk. Ice-dam removal and attic pipe repair are phone calls, not weekend projects.
If a Pipe Bursts: Safety First, Then the First 60 Seconds
Stop: Three Hazards That Outrank the Water
The instinct is to run toward the leak. Check these three things first — each one can turn a plumbing problem into a medical emergency, and none of them take more than a few seconds to assess from a safe distance.
- Water plus electricity. If water is spraying, dripping, or pooling near the electrical panel or a subpanel, near outlets or a plugged-in appliance, or coming through a ceiling light or fan — do not step into the water and do not touch the panel. Energized water and a wet floor can put current through you before you reach the breaker. Get everyone out of that area, cut power at a dry, remote panel only if you can reach it standing on a dry surface with dry hands, and otherwise call your electric utility or a licensed electrician to kill the service. This takes priority over the water main: if your shutoff is inside a flooded electrical area, leave it alone and call the water utility to shut the line at the curb stop instead.
- Bleeding, scalds, or falls. A split copper line leaves edges like a razor, a hot-water burst sprays water hot enough to scald in seconds, and wet floors are how people break wrists during cleanups. Treat the person before the pipe: firm direct pressure with a clean cloth on a cut; 20 minutes of cool (not ice-cold) running water on a scald. Call 911 for bleeding that spurts, soaks through cloth, or won’t stop after 10 minutes of continuous pressure — and for any burn that blisters widely, involves the face or hands, or leaves the skin white or leathery. Water damage can wait 15 minutes. A bleed can’t.
- Gas. If you smell gas, or the burst has soaked a gas furnace or water heater, leave the building without touching switches and call the gas emergency number or 911 from outside. Don’t relight anything yourself.
Then Move Fast
- Shut off the water main. Turn a gate valve clockwise until it stops, or give a ball valve lever a quarter turn.
- Open the lowest faucets in the home to bleed off remaining pressure.
- Cut power to the affected circuits — but only from a dry standing position at a dry panel, per the hazard check above. When in doubt, leave it to an electrician.
- Call a licensed plumber. If you rent, call the emergency maintenance line immediately, then follow up by email.
- Document everything with time-stamped notes and photos before you start cleanup: what you found, when, and where. Insurers will ask — but only photograph what you can reach safely.
For context on the stakes: water damage and freezing rank among the most common and most expensive homeowners insurance claims, and a single burst pipe can mean weeks of drying, demolition, and repair. A $4 foam sleeve and an overnight trickle that costs a dime are a very good trade.
The One-Page Version
- Above 40°F: disconnect hoses, find the shutoff, buy supplies. No dripping.
- 33–40°F: faucet covers on, insulate what you can reach. No dripping.
- 25–32°F: garage closed, thermostat 65°F or higher, exterior-wall sink cabinets open at dusk and closed once the next morning clears 32°F. Still no dripping — unless it’s windy or the freeze will last more than 24 hours.
- 20–25°F: start the overnight trickle at your most exposed tap; run it until the outdoor temperature is back above freezing.
- 10–20°F: trickle everything on exterior walls, hot and cold, no night setback.
- 0–10°F: steady trickle, run water every 4–6 hours, heat cable energized.
- Below 0°F: recheck every 3–4 hours; drain the system if the home will be empty.
Frozen pipes are one of the rare home risks where prevention is nearly free and failure is expensive. Ten minutes tonight beats a plumber, a restoration crew, and an insurance claim.
Frequently Asked Questions
At exactly what temperature do pipes freeze?
Water freezes at 32°F (0°C), but pipes inside a building lag well behind the outdoor air. The standard planning figure is the 20°F (-6.7°C) “temperature alert threshold” for uninsulated pipes in unheated spaces, a number widely attributed to Building Research Council research at the University of Illinois. It’s a guideline, not a guarantee — pipes can and do freeze above 20°F, and an exposed spigot or hose bib can freeze in the upper 20s, especially with wind or a hose still attached. That’s why this guide’s dripping trigger is set at 25°F rather than 20°F.
So what do I actually do at 38°F?
Nothing urgent, and definitely no dripping — nothing in your plumbing is close to freezing. Use the evening as your setup window: slip covers over the outdoor spigots, put foam sleeves on any reachable pipe in the garage or crawlspace, close crawlspace vents, and confirm your main shutoff turns. Those jobs are miserable at 22°F and easy at 38°F, which is the only reason the band exists.
How long does it take for a pipe to freeze?
There’s no reliable formula, because it depends on temperature, wind, insulation, how much of the run is exposed, and whether water is moving. As a rough sense of scale: an exposed hose bib can freeze within an hour or two once temperatures fall into the low 20s, and much faster near zero; an uninsulated crawlspace pipe usually takes several hours; a pipe inside an exterior wall of a heated home may last through a single cold night but not through a multi-day freeze. Treat those as illustrative, not predictive — wind and open crawlspace vents shorten every one of them. In practice, the number of consecutive hours below freezing tells you more than the low temperature alone.
Should I drip hot or cold water?
Both, if the fixture allows it. Set a single-handle faucet to the center position so hot and cold lines both move. If you can only pick one, pick cold — it’s usually the longer, less protected run — but don’t assume hot lines are safe.
Does leaving cabinet doors open really help — and when do I close them?
Yes, measurably. Under-sink cabinets on exterior walls are little dead-air pockets that can sit well below room temperature. Opening the doors lets heated room air reach the pipes. Open them at dusk on any night forecast to drop below 32°F, leave them open through the night, and close them the next morning once the outdoor temperature is back above freezing and climbing. Put a thermometer inside and test it yourself — it’s the cheapest experiment in this article. If you have kids or pets, move cleaning products out of the open cabinet first, and never store bleach alongside ammonia-based cleaners anywhere; mixing them releases toxic gas.
Do I need to insulate pipes if my apartment is always heated?
Interior pipes in a consistently heated apartment are low risk. Concentrate on the weak points instead: a kitchen sink on an exterior wall, a laundry closet with an exterior door, a bathroom on an outside corner, and any unit sitting above an unheated garage. Sleeves are cheap enough that wrapping the few reachable pipes in those spots is still worth the half hour — 3/8 in. wall is plenty for interior cabinet runs anywhere in the country.
Will a smart thermostat or leak sensor prevent a burst?
Sensors prevent damage, not freezing. A leak sensor with a freeze alert tells you a space is getting dangerously cold while there’s still time to act, which is genuinely valuable if you travel — just check the model’s alert temperature so you know how early it speaks up. An automatic shutoff valve on the main goes further: it closes the water supply when it detects abnormal flow, the single most effective way to limit damage in an empty home. Budget for the device plus a plumber’s time, and note that main-line work is generally off the table for renters.
Water pressure dropped at one faucet on a cold night. What now?
Treat it as a forming ice plug and act immediately. Leave that faucet open, warm the space around the suspected pipe, open nearby cabinets, and raise the thermostat. Check other fixtures to map how far the problem extends. If flow stops entirely, or you see a bulge, frost, or moisture, shut off the main and call a licensed plumber instead of experimenting.
Who pays if a pipe bursts in a rental?
It depends on your lease and your jurisdiction, but generally the landlord is responsible for the building and its plumbing, while your renter’s insurance covers your belongings. Tenants get blamed when the heat was turned off or a known cold-room complaint was never reported. That’s precisely why the written report and the 55°F minimum setting matter — they put the record on your side.
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