Most Likely Causes (Ranked)
Pipes running through exterior walls are the #1 burst location. If insulation is thin or missing between the pipe and the exterior sheathing, temperatures inside the wall can drop below 20°F even when the house is heated. Water freezes, expands 9% by volume, and generates up to 25,000 PSI — far exceeding what any pipe can withstand. Copper splits lengthwise. CPVC shatters. Even PEX can burst at fittings.
Pipes in unheated garages, crawl spaces, and attics are exposed to ambient outdoor temperatures. Crawl spaces are especially dangerous because pipes may be insulated when installed but insulation deteriorates or falls off over time. Attic pipes for ice makers, bathroom additions, or HVAC equipment freeze when temperatures stay below 28°F for extended periods.
The rim joist (where the floor framing meets the foundation) is one of the least insulated areas in most homes. Pipes running near or through the rim joist are exposed to nearly outdoor temperatures. This is where the main water line often enters the house, making it a high-impact freeze location.
When homeowners leave for vacation and set the thermostat below 55°F, or when the furnace fails during a cold snap, interior temperatures can drop enough to freeze pipes — even in interior walls if the cold persists long enough. This is especially common in vacant or foreclosed homes.
Outdoor pipes, hose bibs with connected hoses, and pipes in vented crawl spaces experience wind chill that accelerates freezing. A 32°F day with 20 mph wind creates a wind chill of 24°F on exposed pipes. Hose bibs with connected hoses trap water that freezes and propagates into the wall.
How to Fix It
Emergency Response (First 10 Minutes)
Critical- 1IMMEDIATELY turn off the main water shut-off valve. Every minute matters — a burst pipe releases 3-5 gallons per minute.
- 2Open faucets downstream of the burst to relieve pressure and drain remaining water.
- 3Turn off electricity to affected areas if water is near electrical outlets, panels, or appliances.
- 4Move valuables and furniture away from the water. Start extracting standing water with a wet vac.
- 5Call your insurance company's emergency line. Document everything with photos and video.
Thaw Frozen (Not Yet Burst) Pipes
$0-20 DIY- 1If you've found a frozen pipe that hasn't burst yet: leave the faucet open so water can flow as it thaws.
- 2Apply heat with a hair dryer, heat lamp, or electric heating pad wrapped around the pipe. Work from the faucet toward the frozen section.
- 3NEVER use an open flame (torch, propane heater) — fire hazard and it can cause the pipe to burst from sudden thermal shock.
- 4Thawing typically takes 30-60 minutes. If the pipe is behind a wall, point a space heater at the wall.
Repair the Burst Pipe
$10-50 DIY / $200-600 Pro- 1Once thawed and the water is off: locate the burst. Copper will have a lengthwise split. PEX may have a crack at a fitting.
- 2Cut out the damaged section. For copper: use a SharkBite push-fit coupling ($12-15 each) for fastest repair. For PEX: use a PEX crimp or expansion coupling.
- 3For an emergency temporary repair: a pipe repair clamp ($8-15) with rubber pad can stop the leak until a permanent fix is made.
- 4Test the repair by slowly opening the main valve. Check all other pipes for damage — multiple bursts are common.
When to Call a Professional
A burst pipe in a two-story home can cause $20,000-50,000+ in damage. Speed of shutoff is everything.
Never use a torch to thaw pipes — house fires from pipe thawing are more common than you'd think.
Check ALL pipes after a freeze, not just the one that burst. Ice in one pipe means others were likely frozen too.
If the burst is behind a wall or in a ceiling, the drywall must be opened within 48 hours to prevent mold.
Standing water + insulation = mold factory. Remove wet insulation immediately.
How to Prevent It
Insulate all pipes in exterior walls, crawl spaces, attics, and garages with foam pipe insulation ($0.50-2/ft).
Disconnect all hoses from hose bibs before the first freeze — this is the #1 preventable freeze cause.
During extreme cold: open cabinet doors under sinks on exterior walls. Let faucets drip at a pencil-lead stream.
Never set the thermostat below 55°F when leaving the house, even on vacation.
Seal air gaps around pipes where they penetrate exterior walls with spray foam ($5-8/can).
Frequently Asked Questions
Usually yes for sudden and accidental bursts. The water damage to the home is covered. The pipe repair itself typically isn't. Deductibles are $1,000-2,500 on most policies. Negligence (leaving heat off in a vacant home) may void coverage.
Average insurance claim: $10,000-15,000. Worst case (undetected for hours/days): $50,000-100,000+. The water itself causes immediate damage; mold remediation adds $2,000-20,000.
Water freezes at 32°F, but pipes in exterior walls can burst when outdoor temps hit 20°F. Pipes in uninsulated areas freeze faster. Wind chill accelerates freezing on exposed pipes.
PEX is more freeze-resistant because it can expand slightly. But PEX still bursts at fittings and under severe freezes. Neither is freeze-proof — insulation and heat are the only real protection.