What to Do Immediately When a Frozen Pipe Bursts
Quick answer
When a frozen pipe bursts, shut off your home's main water valve within the first few minutes, then remove standing water and call a restoration company. Mold can start in 24 to 48 hours. Repair alone averages $500, and insurance usually covers the water damage, not the pipe, if you kept the home at 55F or warmer.
Key takeaways
- Water expands about 9% as it freezes, and that pressure buildup is what splits a pipe, according to COIT Restoration; shutting off the main valve in the first few minutes limits how much escapes afterward.
- Meaningful freeze risk starts at 20F or colder; an insulated pipe can still freeze in about 6 hours at that temperature, and an uninsulated exterior pipe in 4 to 8 hours, per American Family Insurance and Family Handyman, building on long-cited University of Illinois field testing.
- National average burst-pipe repair runs about $500 ($200 to $1,000); once a pipe has burst, replacing the damaged section adds $400 to $1,200, or $600 to $5,000 or more if it's underground or under a slab, according to FIXR.
- Frozen pipes account for 22.6% of homeowner insurance losses, with an average payout of $15,400, and 29.4% of all homeowner claims filed, per the Insurance Information Institute and Family Handyman.
- Mold can begin growing within 24 to 48 hours of standing water, per the EPA, so drying needs industrial equipment, not just open windows and a fan.
On this page
- First-Hour Emergency Steps When a Frozen Pipe Bursts
- How Much Water Does a Burst Frozen Pipe Release?
- At What Temperature Do Pipes Freeze, and How Long Until They Burst?
- Where Are Frozen Pipes Most Likely to Burst in Your Home?
- Why Does a Frozen Pipe Sometimes Not Leak Until Hours Later?
- Can You Thaw a Frozen Pipe Yourself, or Do You Need a Plumber?
- How Much Does Frozen Pipe Repair Cost?
- Is Frozen Pipe Damage Covered by Homeowners Insurance?
- How Do You Prevent This From Happening Again?
- When to call a professional
- Frequently asked questions
First-Hour Emergency Steps When a Frozen Pipe Bursts
When a frozen pipe bursts, shut off your home's main water valve within the first few minutes, then check the rest of the house before you call for help. One hard freeze often cracks more than one pipe, so a second leak can show up once the heat comes back on.
- Shut off the main water valve, usually near the foundation, the water meter, or in a basement; turn it clockwise until it stops.
- If the valve is stuck, call your water utility to shut off service at the curb instead of forcing it.
- Walk through exterior walls, the crawlspace, the attic, and the garage, checking for frost or a second break before you relax.
- Remove standing water with towels or a wet/dry vacuum, and move dry belongings away from the wet area.
- Call a water restoration company, not just a plumber. You need water extraction and industrial drying, and a plumber alone won't stop mold from starting.
- Photograph all the damage before cleanup begins, for your insurance claim.
Never point a blowtorch, propane heater, or open flame at a pipe you suspect is still frozen; sudden heat can crack it further or start a fire. For the full first-hour sequence, including when it's safe to cut your own power, see what to do when any pipe bursts.
If you don't already know where yours is, see how to find your main water shutoff valve.
How Much Water Does a Burst Frozen Pipe Release?
A burst pipe keeps flowing at full household water pressure until you shut off the main valve, so even a short delay can soak a large area. That's why shutting off the main valve in the first few minutes matters more than anything else you do.
Every extra hour means more area to dry and less time before mold risk sets in. The EPA says wet materials need to dry within 24 to 48 hours of a leak or mold is likely to start, and the restoration industry's IICRC S500 standard uses that same window as its benchmark.
| Time Since the Burst | What You're Likely Dealing With |
|---|---|
| Under 1 hour | Visible pooling in the room where the pipe broke; still removable with towels or a wet/dry vacuum |
| 24 to 48 hours | The EPA and IICRC S500's critical window; anything still wet past this point is likely growing mold |
| 3 to 5 days | Typical length of professional drying and dehumidification once extraction starts, per COIT Restoration |
| 2 weeks or longer | Full restoration timeline for severe damage, including drywall, flooring, or insulation replacement, per COIT Restoration |
An open supply line can soak drywall, insulation, and subfloor in rooms far from the original break within hours. That's why a restoration company needs to start extraction while the plumber is still working on the pipe itself.
At What Temperature Do Pipes Freeze, and How Long Until They Burst?
Water freezes at 32F, according to Bob Vila, but meaningful freeze risk for household pipes doesn't start until about 20F or colder, per the International Code Council as cited by Family Handyman. Below that line, how fast a pipe actually freezes depends on insulation, material, and location.
| Outdoor Temperature | Insulated Pipe | Uninsulated or Exterior Pipe |
|---|---|---|
| 20F to 32F (mild freeze) | About 12 hours | 6 to 8 hours |
| Below 20F | About 6 hours | 4 to 6 hours |
Industry estimates suggest extreme cold, below 10F, can shorten an exposed pipe's freeze time to roughly 2 to 4 hours, though that figure is less firmly documented than the ranges above.
Water expands about 9% as it freezes, according to COIT Restoration, and that expansion builds the pressure that splits a pipe wall.
Copper conducts heat away fastest of the common pipe materials, so copper pipes freeze first and are the most vulnerable to rupture, according to Family Handyman. PEX and PVC freeze too, but their plastic walls flex more and don't always rupture.
Not every frozen pipe bursts; a slow freeze in a well insulated space can sometimes release pressure through a small crack instead of a full rupture.
Where Are Frozen Pipes Most Likely to Burst in Your Home?
Pipes freeze first wherever they sit closest to outdoor cold with the least insulation: exterior walls, unheated attics, crawlspaces, garages, unheated basements, and outdoor spigots. A pipe in any of these spots deserves extra attention before a hard freeze.
| Location | Why It Freezes First |
|---|---|
| Crawlspace | Unheated, poor air circulation, and often the hardest place to spot a leak before major damage sets in |
| Exterior wall (kitchen or bathroom cabinets) | Pipe runs sit close to outside cold with little insulation around them |
| Unheated attic | No heat source, and often minimal insulation around the pipe itself |
| Garage | Rarely heated, and often has an uninsulated exterior wall or door |
| Unheated basement | Colder than living space, especially near rim joists and foundation walls |
| Outdoor spigots and hose bibs | Directly exposed to outdoor air, with no insulation at all |
A pipe in a crawlspace generally costs more to repair and dry than one in a basement utility room, simply because reaching it, drying the subfloor, and confirming it's actually dry all take longer. The full cost breakdown is below.
If the burst happened in a crawlspace, check these before you consider it handled:
- Standing water fully removed, not just what you can see from the access hatch
- Subfloor doesn't feel soft, spongy, or bouncy when you press on it
- A moisture meter reads dry, not just surface-dry, before insulation or flooring goes back
- No musty smell lingering after the space has had time to air out
See what water damage restoration typically costs for the broader room-by-room picture beyond frozen-pipe repairs.
Why Does a Frozen Pipe Sometimes Not Leak Until Hours Later?
A pipe can crack while it's still frozen without leaking at all, because the ice blockage itself plugs the break. Water only starts pouring out once the ice melts and pressure returns, sometimes well after you've turned the heat back up.
This is why a homeowner can raise the thermostat after a cold snap, think the danger has passed, then find water pouring from a wall or ceiling later that same day. The pipe already split during the freeze; the leak just hadn't shown up yet.
Check walls, ceilings, and cabinets near any pipe that froze during a cold snap, even once temperatures rise again. A damp spot, a new stain, or a soft patch of drywall can be the first sign of a break that happened hours earlier.
Can You Thaw a Frozen Pipe Yourself, or Do You Need a Plumber?
You can often thaw a pipe yourself if it's accessible and hasn't burst yet. Once it has burst, you need a plumber for the repair and a restoration company for the water, not a space heater.
Safe Thawing Methods, Ranked by Risk
- Electric heating pad or heat tape: wrap it around the pipe and let it warm gradually. Lowest risk of the options here.
- Hot-water-soaked towels: wring out a towel in hot water and wrap it around the frozen section, refreshing it every few minutes. Slow, but safe.
- Hair dryer on high heat: aim it at the frozen section, working from the faucet end toward the blockage. Fine for light surface frost.
- Portable space heater: keep it several feet away from the pipe and never leave it unattended; higher risk than the methods above because it heats the whole area, not just the pipe.
Never Use These
- Open flames, candles, or matches
- Blowtorches or welding torches
- Propane or butane heaters pointed directly at a pipe
- Boiling water poured straight onto a frozen section; the sudden heat can crack the pipe further
If you call a plumber just to thaw a line that hasn't burst, expect a flat-fee service call of around $100. Once a pipe has actually split, that fee changes to a repair job instead; see what burst pipe repair typically costs for the full breakdown.
Don't try to thaw a section you think may already be cracked. Applying heat near a hidden break can push more water out before you or the plumber are ready for it.
How Much Does Frozen Pipe Repair Cost?
National average burst-pipe repair runs about $500, with most jobs costing $200 to $1,000, according to FIXR and Angi. Once a pipe has actually ruptured, replacing the damaged section typically adds $400 to $1,200 depending on how hard it is to reach.
| Service | Typical Cost |
|---|---|
| Thawing only, pipe hasn't burst | Around $100 flat fee |
| Burst-pipe section replacement, accessible location | $400 to $1,200 |
| Underground or slab-embedded burst | $600 to $5,000 or more |
Labor makes up $300 to $400 of a typical $500 repair bill, and plumbers charge $45 to $200 an hour depending on where you live, according to FIXR.
Underground and slab-embedded pipes cost the most because they're an excavation job, not just a repair: locating the break, digging down, replacing the section, and backfilling all take far more labor than an exposed basement pipe.
Ask about trenchless repair (relining instead of a full trench); it isn't always cheaper, but it means less digging.
Is Frozen Pipe Damage Covered by Homeowners Insurance?
Most homeowners insurance covers the water damage from a frozen-pipe burst if it was sudden and accidental, according to the National Association of Insurance Commissioners. It typically does not cover the pipe itself, and coverage can be denied if the home wasn't kept heated.
- Usually covered: drywall, flooring, belongings, and professional drying, once the burst itself was sudden and accidental.
- Usually not covered: the pipe repair or replacement itself, and any damage traced to a home left unheated or unwinterized.
- Your deductible still applies. Check your policy for the exact amount you owe out of pocket before coverage kicks in.
American Family Insurance advises keeping your home at 55F or warmer, even while away, as one of the preventive steps insurers expect before they treat a freeze as an accident rather than neglect.
Frozen pipes are a significant share of all homeowner claims: water damage and freezing caused 22.6% of homeowners insurance losses in 2023, with an average payout of $15,400, per the Insurance Information Institute, and insurance-industry data cited by Family Handyman puts frozen-pipe claims at 29.4% of all homeowner claims filed annually.
For the full breakdown of what's covered, deductibles, and how claims get denied, see our complete guide to whether insurance covers a burst pipe. This is general information, not insurance advice; check your own policy or ask your agent about your specific coverage.
How Do You Prevent This From Happening Again?
Keep your home at 55F or warmer year round, even while away, and insulate any exposed pipe in an unheated space. Both are inexpensive compared with a single repair.
Letting a faucet drip during a hard freeze keeps water moving through the pipe most at risk, and opening cabinet doors lets room heat reach pipes behind them.
For the complete room-by-room checklist, including heat tape safety, well-house protection, and what to do before leaving home for the winter, see our full guide to preventing frozen pipes this winter.
When to call a professional
Call a water restoration company right away if:
- Any wall, floor, ceiling, or crawlspace has visible water. The 24 to 48 hour mold window (EPA, IICRC S500) starts as soon as the leak does, not when you notice it.
- Water has spread past the room where the pipe broke, into a hallway, closet, or the room below.
- Water is in a basement or crawlspace, where humidity stays high and drying is hardest without industrial equipment.
- You can't shut off the main valve or it's stuck; call your water utility to shut it off at the curb or meter instead of forcing it.
Call a plumber if:
- The pipe has actually ruptured; thawing alone won't stop an active leak.
- The frozen or burst section is inside a wall, attic, crawlspace, or underground; these all need professional access or excavation.
- You don't know which pipe is frozen or burst; locating it yourself wastes time during the freeze-to-burst window.
You can likely handle it yourself if:
- A pipe is frozen but hasn't leaked yet, and you can reach it directly with an electric heating pad or similar gentle heat.
- Only a small, easily reached puddle sits on tile or concrete, with no drywall, carpet, or insulation nearby.
Frequently asked questions
What's the difference between a frozen pipe and a burst pipe?
A frozen pipe is blocked with ice but hasn't split; water just stops flowing to that fixture. A burst pipe has actually cracked, so water leaks out, sometimes only once the ice inside melts. A burst always needs a plumber. A frozen pipe may thaw safely on its own with gentle heat, but it's worth having a plumber check for small cracks once it fully thaws.
Will a frozen pipe always leak right away, or can it wait until later?
Not necessarily. Many frozen pipes crack while still blocked by ice, but the ice itself plugs the hole, so nothing leaks until the ice melts and water pressure returns. That's why turning the heat back up after a freeze sometimes reveals a leak you didn't know was there. Check walls, ceilings, and cabinets near any pipe that froze, even after the cold snap passes.
Should I try to thaw the pipe myself before the plumber arrives?
Only if the pipe clearly hasn't burst yet; apply gentle heat with an electric heating pad or warm towels, working from the faucet end toward the blockage. If you can't tell whether it's cracked, or the section is hidden inside a wall or crawlspace, wait for the plumber. Thawing a section that's already split can push more water out before anyone is ready for it.
Is the 24 to 48 hour mold window really that fast?
Yes. The EPA and the restoration industry's IICRC S500 standard both set 24 to 48 hours as the window before mold is likely to start on wet materials. Drywall, carpet, insulation, and wood all hold moisture, and warm, humid spots like crawlspaces and enclosed wall cavities grow mold even faster than open rooms.
Will insurance still pay if I didn't winterize before the freeze?
It's unlikely, though not automatic. Insurers generally expect you to have kept the home at 55F or warmer and taken basic precautions like insulating exposed pipes, per American Family Insurance. If an adjuster decides the freeze happened because the home was left unheated or neglected, the claim can be denied entirely. Check your specific policy language, since requirements vary.
Why does an underground or slab leak cost so much more to fix?
Underground and slab-embedded pipes aren't just a repair, they're an excavation job too. A plumber has to locate the exact break, dig down to it, cut out and replace the damaged section, then backfill, which is far more labor than an exposed basement pipe. That's why FIXR puts this repair at $600 to $5,000 or more, versus $400 to $1,200 for an accessible pipe.
Sources
- US EPA, A Brief Guide to Mold, Moisture and Your Home
- National Association of Insurance Commissioners (NAIC), Will My Homeowners Insurance Policy Cover Water Damage / Burst Pipe
- Insurance Information Institute (Triple-I), Facts + Statistics: Homeowners and Renters Insurance
- American Family Insurance, What to Do When Frozen Pipes Burst
- Bob Vila, Frozen Pipes
- Family Handyman, Signs of Frozen Pipes
- FIXR, Burst Pipe Repair Cost
- COIT Restoration, When Frozen Pipes Become Burst Pipes
- IICRC S500 water restoration standard (industry benchmark, secondary-source summary)