How to Prevent Frozen Pipes
To prevent frozen pipes, keep heat reaching your plumbing and stop cold air from getting to it. Most home pipes freeze near 20°F, so insulate exposed lines, seal drafts, hold the thermostat at or above 55°F, and let the faucet farthest from your water main drip during a hard freeze. The most exposed pipes freeze first.
At what temperature do pipes freeze?
Water freezes at 32°F, but most household pipes hold until the air around them drops to about 20°F, the basis for the 20-degree rule. Below 20°F for six hours or more, even insulated pipes are at risk. Poorly insulated pipes in unheated spaces can freeze above 20°F, so exposure matters as much as the temperature.
Freeze timing tracks with the cold. Insulated pipes often take about six hours below 20°F, while pipes in the 20°F to 32°F range may last twelve hours or longer. Exposed lines freeze faster, and near 0°F an unprotected pipe can freeze in minutes.
The pipes most likely to freeze share two traits: little surrounding heat and heavy exposure. Watch these first:
- Outdoor hose bibs, sprinkler lines, and pool supply lines
- Supply pipes in unheated crawl spaces, attics, and garages
- Water lines running inside exterior walls
- Kitchen and bathroom pipes on an outside wall, especially under sinks
How do you prevent frozen pipes?
You prevent frozen pipes by combining a few methods matched to your home. Insulation and sealing cut heat loss year-round, heat cable adds warmth to the coldest runs, and dripping plus a steady 55°F thermostat carries you through a hard freeze. The table below ranks each method by effort, cost, how much it helps, and when to use it.
| Method | Effort and cost | How much it helps | When to use it |
|---|---|---|---|
| Foam pipe insulation (sleeves) | Low, about $2 to $4 per 6 ft, DIY | Strong on exposed lines | Any pipe in an unheated space, year-round |
| Heat tape or heat cable (UL 2049) | Medium, about $30 to $80 plus an outlet, 3 to 7 watts per foot | Strongest for the coldest runs | Pipes that freeze repeatedly, well lines, hose bibs |
| Drip the farthest faucet | Very low, pennies of water per day | Moderate, relieves pressure | During a hard freeze below 20°F |
| Keep thermostat at 55°F or higher | Low, a higher heat bill | Strong | Overnight and while you are away |
| Open cabinet doors | None, free | Modest | Sinks on exterior walls during a freeze |
| Seal gaps and drafts (caulk, spray foam) | Low to medium, about $5 to $15 | Preventive, compounds with the rest | Rim joists, sill plates, and cable or pipe entries |
| Disconnect hoses, cover outdoor faucets | Low, covers about $2 to $10 each | Strong for outdoor bibs | Every fall before the first freeze |
| Keep the garage door closed | None, free | Modest | When supply lines run through the garage |
Handle outdoor faucets before the first freeze. Disconnect hoses, drain the bib, and shut the interior valve if you have one. If a hose bib drips or the stem leaks, our guide to fix or winterize an outdoor faucet walks through packing nuts, washers, and frost-free stems.
Should you drip faucets, and how much?
Yes, drip faucets when the outdoor temperature is expected to stay below 20°F for three hours or more. Open the faucet farthest from where water enters the house to a stream about 1/8 inch wide, roughly pencil-lead thin. Drip both hot and cold sides. Moving water resists freezing and the lower pressure reduces the chance a pipe bursts.
Do pipe insulation and heat tape actually work?
Both work when matched to the pipe. Foam sleeves with a 1/2 to 3/4 inch wall, roughly R-3 to R-4, slow heat loss on any exposed line for a few dollars per length. Self-regulating heat cable rated 3 to 7 watts per foot and listed to UL 2049 adds heat to the coldest runs, such as well lines and hose bibs.
How do you winterize plumbing before leaving town?
If you leave during freezing weather, either keep the heat on at 55°F or higher, or drain the system so nothing can freeze. For a short trip with the heat running, set the thermostat and open interior doors. For a long absence in an unheated home, follow the full drain-down below in order.
- Set the thermostat no lower than 55°F if the heat will stay on.
- If the home will be empty and unheated, shut off the main water valve.
- Open every faucet, tub, and shower, then flush the toilets to drain the lines.
- Drain the water heater and any low-point drains; for a full winterization, blow out the lines with compressed air.
- Pour nontoxic RV or plumbing antifreeze into every drain trap and into each toilet bowl and tank.
- Disconnect hoses, drain and cover outdoor faucets, and shut any interior hose-bib valves.
- Open interior cabinet and closet doors so residual heat can reach the pipes.
- Ask a neighbor to check the home during any extended cold snap.
Fold these steps into your fall routine so nothing gets missed. Our seasonal plumbing maintenance checklist lists the insulation, sealing, and shutoff tasks to finish before the first hard freeze.
What if a pipe freezes anyway?
If a faucet slows to a trickle during a freeze, a pipe is likely frozen and needs attention before it splits. Keep that faucet open, find the frozen section, and warm it slowly. Our guide on how to thaw a frozen pipe safely covers the right heat sources and what to avoid.
A frozen pipe that has already cracked can flood a room in minutes once it thaws. Know where your main shutoff is before winter. If a line lets go, our steps for what to do when a pipe bursts cover the first ten minutes and the insurance paperwork that follows.
Frequently asked questions
At what temperature do pipes freeze?
Water freezes at 32°F, but most household pipes hold until the air around them falls to about 20°F. That gap is why plumbers use the 20-degree rule. Uninsulated pipes in exterior walls, crawl spaces, attics, and garages can freeze above 20°F, so location matters as much as the number on the thermometer.
How long does it take for pipes to freeze?
It depends on temperature and insulation. Below 20°F, insulated pipes often freeze in about six hours, while pipes between 20°F and 32°F may take twelve hours or more. Exposed lines freeze faster, and near 0°F an unprotected pipe can freeze in minutes. Sustained cold, not one brief dip, does the damage.
Should I drip my faucets, and which ones?
Yes, drip faucets when the outdoor temperature is expected to stay below 20°F for three hours or more. Open the faucet farthest from where water enters the house to a stream about 1/8 inch wide, roughly pencil-lead thin. Drip both hot and cold. Moving water resists freezing and lower pressure reduces burst risk.
What temperature should I keep my house to avoid frozen pipes?
Keep the thermostat at or above 55°F, day and night, and hold that same setting while you are away. A steady 55°F keeps heat reaching pipes inside walls and cabinets. Dropping the heat overnight to save money often costs far more if a pipe freezes, splits, and floods a room.
Which pipes freeze first?
Pipes with the least heat and the most exposure freeze first: outdoor hose bibs, sprinkler and pool lines, and supply pipes running through unheated crawl spaces, attics, garages, and exterior walls. Kitchen and bathroom lines on an outside wall are common indoor culprits. Insulate or heat-tape these before an interior line in a warm core.
Should I shut off the water if I leave for the winter?
If the home will sit empty and unheated, yes. Shut the main valve, open every faucet, flush the toilets, and drain the water heater and low points so nothing is left to freeze. For a full winterization, blow out the lines with compressed air and add nontoxic antifreeze to drain traps and toilets.
Last reviewed: September 2026.