How to Protect Pipes During a Hard-Freeze Warning (4 Steps)

TL;DR: Open cabinet doors under sinks, let faucets drip at pencil-lead width, insulate exposed pipes in crawl spaces and attics, and shut off outdoor hose bibs. A burst pipe costs $5,000–$10,000 in repairs; these four steps take under an hour and cost almost nothing.

_Last reviewed: July 2026 · 6 min read_

When the National Weather Service issues a hard-freeze warning—typically for temperatures at or below 28°F for several hours, often dipping into the teens—your plumbing is at risk. Water expands 9% when it freezes, and that expansion can split copper, PVC, or PEX in minutes once the temperature inside the pipe drops far enough. The resulting flood often goes unnoticed until the thaw, when pressurized water sprays into walls, ceilings, or basements.

Okoniq Property Hub logs your winterization steps and photo evidence of insulated pipes, so you have a timestamped record if an insurance claim arises later.

What temperature causes pipes to burst?

Pipes typically burst when the ambient temperature stays below 20°F for six hours or more, especially if wind chill accelerates heat loss. Pipes in unheated attics, crawl spaces, exterior walls, or uninsulated garages are most vulnerable. A 2018 Insurance Institute for Business & Home Safety study found that the majority of freeze claims occur when outdoor temps drop to 20°F or below and the pipe is in an unconditioned space with minimal airflow.

Southern homes face higher risk because construction codes in warm climates often route pipes through exterior walls or uninsulated crawl spaces that would be buried or interior runs in the North. If you manage properties in Texas, Louisiana, or the Carolinas, a single-digit night can cause hundreds of claims in a metro area that rarely sees such cold.

Indoor pipes rarely freeze unless the thermostat is off or set below 55°F. If you're closing a seasonal home for winter, draining the system entirely is the only reliable protection; a drip won't help if the furnace is off.

How do I insulate exposed pipes before a freeze?

Start in the crawl space, attic, and garage—anywhere pipes run through unconditioned air. Foam pipe sleeves (closed-cell polyethylene) cost $1–$3 per six-foot length at any hardware store and slip over copper or PEX in seconds. Slit the sleeve lengthwise, slide it on, and tape the seam with foil or duct tape. For elbows and tees, cut sleeves at 45° angles and tape the joints.

Fiberglass pipe wrap is an alternative for irregular runs or cast-iron drains, though it's less effective than foam if it gets damp. If you've dealt with cast iron drain pipe replacement, you know those older lines in crawl spaces corrode from the outside; foam sleeves won't fix rust but they will slow heat loss.

Heat tape (also called heat cable) is a low-wattage electric wire you spiral around the pipe and plug in when a freeze is forecast. It's overkill for a one-night event but worth the $30–$50 investment if you have a run that freezes every winter. Always follow the manufacturer's installation guide—improper overlap can overheat PVC.

Outdoor hose bibs deserve special attention. Disconnect and drain garden hoses, then close the interior shutoff valve if your home has one. Open the exterior faucet to let residual water drain, and leave it cracked. Some landlords install foam faucet covers ($3 each) over the spigot for extra insulation.

Should I let faucets drip, and which ones?

Yes—a drip relieves pressure and keeps water moving, which delays freezing. You don't need every faucet running; focus on fixtures fed by pipes in exterior walls or unheated spaces. A pencil-lead-width stream (roughly 5 drips per second) is enough. Both hot and cold sides should drip if a single pipe run serves both; in most homes, opening the hot tap slightly will pull from the water heater and keep both lines moving.

Prioritize the kitchen sink if it backs to an exterior wall, bathroom sinks on outside corners, and any utility sink in an unheated garage. A dripping faucet wastes 1–2 gallons per day—about 6 cents of water and 12 cents of sewer in most US cities—but a burst pipe repair starts at $500 for a simple PEX splice and reaches $10,000 if drywall, flooring, and ceiling water stain repairs are needed.

Stop the drip once daytime highs return above freezing and nighttime lows climb above 28°F. If you leave it running for a week, you've spent a few dollars on water but avoided a five-figure insurance claim.

What else can I do to protect plumbing during a hard freeze?

Open cabinet doors under sinks to let warm room air reach the pipes. Kitchen and bathroom vanities trap cold air, especially if the cabinet backs to an exterior wall. A simple bi-fold door left ajar overnight can raise the pipe temperature 10–15°F, enough to prevent freezing when the outdoor temp is borderline.

Set your thermostat to at least 55°F if you'll be away, and leave interior doors open so heat circulates evenly. Closing off spare bedrooms or bathrooms to "save energy" creates cold pockets where pipes can freeze. The cost of keeping a 1,500-square-foot home at 55°F for three winter days is roughly $15–$25, depending on your heating fuel; a burst pipe will cost 200 times that.

Check your water heater location. If it's in an unheated garage or basement, wrap the tank in an insulating blanket (about $30 at home centers) and insulate the first six feet of hot- and cold-water pipes leading from the unit. Some codes now require this in new construction, but older homes often have bare copper in garages.

If your property has a slab foundation and the freeze is expected to last more than 24 hours, keep water moving by running a washing machine load or flushing toilets periodically. Slab homes in Texas and Arizona have seen under-slab supply lines freeze during historic cold snaps (February 2021 in Texas being the worst example).

What should I do immediately after a hard freeze passes?

Walk the property once temps climb above freezing. Check ceilings, crawl spaces, and the area around the water heater for wet spots or drips. Listen for the hiss of running water when all fixtures are off—a sign of a pinhole leak inside a wall. If you find a spray or a puddle, shut off the main water valve immediately, then call a plumber.

Document everything with photos before the water spreads. Okoniq Property Hub timestamps and geo-tags each image, which insurance adjusters appreciate when claims involve multi-unit properties or long discovery delays. Some leaks don't announce themselves until the next time you turn on a faucet and water sprays from a cracked fitting.

If you turned off the main water supply as a precaution, restore it slowly. Open the valve a quarter-turn every few minutes while someone watches for leaks at fixtures, under sinks, and at the water heater. A sudden pressure spike can blow a weakened joint that survived the freeze itself.

Landlords with vacant units should walk each one within 24 hours of a hard freeze. Tenants often don't notice a slow drip from a ceiling until drywall sags or mold appears—by then the repair bill has doubled. Properties battling attic mold from a past roof leak are especially vulnerable to secondary moisture damage if a freeze splits an attic supply line.

FAQ

How cold does it have to be inside a house for pipes to freeze?

Indoor pipes typically freeze when interior air temperature drops to 32°F or below for an extended period, which happens if the furnace fails or the thermostat is set too low. Pipes in exterior walls can freeze even when the living space is above 55°F if there's no insulation between the pipe and the outdoor cold.

Can PEX pipes burst during a freeze?

PEX is more freeze-tolerant than copper because the tubing can expand slightly, but it's not freeze-proof. Ice blockages in PEX can still burst fittings—especially brass connections—and the tubing itself will split if the expansion exceeds its elastic limit. Insulate PEX runs in unconditioned spaces just as you would copper.

Is it better to drip hot or cold water?

Drip both if possible, but the cold side is the priority because cold-water pipes often run along exterior walls and are more exposed. The hot-water line usually benefits from residual heat radiating off the water heater, so it's less likely to freeze unless it runs through an attic or crawl space far from the heat source.

How much does pipe insulation cost for a whole house?

Foam sleeves run $1–$3 per six-foot section; insulating 100 linear feet of pipe costs $15–$50 in materials and takes two to three hours of DIY labor. Professional installation for a 2,000-square-foot home typically runs $200–$400 if the plumber does a crawl-space and attic retrofit at the same time.

Should I shut off water to a vacant rental during a freeze?

Yes, and drain the lines by opening all faucets after shutting the main valve. Pour RV antifreeze (not automotive antifreeze) into each drain trap—including toilets, sinks, and floor drains—to prevent the trap water from freezing and cracking. If you can't drain the system, keep the heat at 55°F minimum and let a faucet drip.

This is educational information, not plumbing or engineering advice. For properties with complex heating systems, shared risers, or commercial occupancy, consult a licensed plumber before a freeze event to tailor protection to your specific building envelope.