Frozen Pipes
Updated February 20, 2026
Water freezing inside a pipe generates over 2,000 PSI -- enough to split copper, PEX, or PVC. Pipes in exterior walls, crawl spaces, attics, and garages are most vulnerable. Quick thawing before a burst saves thousands.
Overview
When temperatures drop below 20 degrees, exposed pipes can freeze solid. The danger is not the ice -- it is the pressure buildup between the blockage and the closed faucet. That pressure bursts pipes, often away from the actual freeze point. One burst pipe releases hundreds of gallons per hour. Prevention first, early detection second, safe thawing if a freeze happens. This guide covers all three, plus what to do if a pipe has already burst.
Symptoms
- No water or only a trickle from a faucet, especially on an exterior wall
- Some faucets work fine, others do not -- localized freeze
- Visible frost or ice on exposed pipes in basement, crawl space, garage, or under cabinets
- Bulge or crack visible on an exposed pipe section
- Clanking or banging when you turn on the water -- ice shifting inside
- Wet spots on walls, ceilings, or floors near pipe runs -- pipe may have already burst behind the wall
Common Causes
- Pipes in uninsulated exterior walls -- most common location. Builders run supply lines through exterior walls for convenience, but without insulation they are directly exposed to outside temperatures.
- Unheated spaces -- crawl spaces, attics, garages. Any pipe not maintained above freezing is at risk. Vented crawl spaces are especially vulnerable.
- Thermostat too low during cold snaps or power outages -- interior drops below 55 degrees and pipes in walls and cabinets freeze, especially during sustained sub-zero.
- Garden hose left attached in winter -- traps water in the hose bib and supply pipe behind it. Freezes and cracks the bib or splits the pipe inside the wall.
- Gaps at rim joists and foundation penetrations -- cold air blows directly onto pipe surfaces, creating localized freezing even when the rest of the house is warm.
What You'll Need
How to Fix It
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Confirm the Pipe Is Frozen (Not Burst)
Turn on the affected faucet, both hot and cold. Nothing or a trickle means frozen. Other faucets working? Freeze is localized. Inspect exposed pipes in basement, crawl space, and under exterior-wall cabinets. Look for frost, bulging, cracks. Water spraying, dripping from the ceiling, or pooling? Pipe has already burst -- skip to emergency steps.
Tip: Not sure where the freeze is? Feel exposed pipes. Frozen section is noticeably colder than surrounding pipe and may have a slight bulge. -
Open the Faucet Before You Start Thawing
Before any heat, open the faucet the frozen pipe feeds -- both hot and cold. Critical step. As ice melts, the open faucet relieves pressure and gives water somewhere to go. Even a trickle helps melt ice from the inside.
Warning: Never thaw with the faucet closed. Heating a sealed pipe builds steam pressure that can cause explosive failure. -
Thaw Exposed Pipes Safely
Start from the faucet end, work back toward the freeze. This lets melting water flow out the open faucet. Hair dryer on high, moving back and forth. Heat lamp or space heater aimed at the area. Or wrap with hot-water-soaked towels, replacing as they cool. Continue until full pressure is restored.
Warning: Never use an open flame -- torch, propane heater, charcoal. Fire hazard, can fail soldered joints, melts PVC. Hair dryer or heat lamp only. -
Thaw Pipes Inside Walls
Pipe in a wall? Turn up the thermostat. Open cabinet doors under the affected sink to let warm air in. Space heater aimed at the wall. Infrared thermometer to find the coldest spot -- that is the freeze. Severe cases: cut an access hole in the drywall for direct heat. Last resort but can prevent a burst.
Tip: Fan blowing warm room air into the open cabinet space significantly speeds up thawing. -
If the Pipe Has Already Burst
Water spraying or flooding? Immediate action. Main water shutoff -- near the meter or where the main enters the building. Cannot find it? Shut off the well pump. Open all faucets to drain the system. Kill electricity to any area where water contacts outlets, fixtures, or panels. Call a plumber. Start mitigation: extract water, fans, dehumidifiers, move belongings.
Warning: Water near your electrical panel? Do not touch it. Call your electric utility to disconnect at the meter. Water and electricity are lethal. -
Inspect All Pipes After a Freeze Event
After the crisis, inspect all exposed pipes for cracks, bulges, or pinholes. Check joints, elbows, direction changes -- weak points. Water back on slowly, walk through the house checking every sink, basement, crawl space. Some bursts do not leak until ice melts and pressure returns. Post-thaw inspection is essential.
Tip: Had a burst? Check your homeowner's insurance. Most policies cover sudden burst-pipe damage. They typically do not cover gradual leaks or negligence (leaving the house unheated).
When to Call a Pro
Call a plumber immediately if a pipe has burst, if you cannot find the frozen section, if the pipe is in a wall or ceiling you cannot access, if thawing has not worked after several hours, or for any burst repair. Many plumbers offer emergency service during freeze events. Also for frost-proof hose bibs, rerouting vulnerable pipes, or installing heat trace cable.
Prevention Tips
- Insulate all pipes in unheated areas with foam sleeves or fiberglass wrap. Single most effective prevention, under $1 per linear foot.
- Disconnect garden hoses before the first freeze. Close the interior shutoff for each hose bib, open the outdoor faucet to drain. Consider frost-proof bibs.
- Thermostat at 55 degrees or higher when away in winter. Never turn the heat off completely in a home with plumbing.
- Extreme cold: open cabinet doors under exterior-wall sinks to let warm air circulate around the pipes.
- Pencil-thin drip from faucets on exterior walls during sustained sub-zero. Moving water is much harder to freeze.
- Seal gaps at rim joists, foundation penetrations, and pipe entry points. Cold air blowing directly on pipes causes localized freezing.
- Pipes that freeze repeatedly? Heat trace cable with an automatic thermostat. Definitive solution.