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How long does it take pipes to unfreeze naturally?

Frozen pipes can be a major inconvenience, leaving you without running water until they thaw. If your pipes freeze, you may be wondering how long it will take for them to unfreeze on their own. The answer depends on several factors.

What causes pipes to freeze?

Pipes usually freeze when the temperature drops below freezing, 32°F (0°C). The water inside the pipes freezes and expands, putting pressure on the pipe walls. If the pressure builds up too much, the pipe can burst. Pipes are most likely to freeze when they are exposed to very cold temperatures for an extended time, such as during a cold snap or polar vortex.

Certain conditions make pipes more prone to freezing:

  • Pipes in unheated indoor spaces like basements, crawl spaces, attics, or garages
  • Pipes running against exterior walls with little insulation
  • Drafts from doors, windows, or openings that allow cold air to reach pipes
  • Low water usage that allows water to sit stagnant and freeze more readily
  • Old, corroded, or damaged pipes in need of repair

Factors that affect thawing time

Several key factors affect how long it takes for frozen pipes to thaw:

Temperature

The warmer the temperature, the quicker frozen pipes will thaw. At 50°F or higher, thawing can occur within a day. At lower temperatures closer to freezing, it can take several days or longer.

Pipe size and water volume

Larger diameter pipes and greater water volume will retain more thermal mass, taking longer to thaw. Smaller pipes or sections with lower water volume will thaw faster.

Pipe material

Metal pipes conduct cold better than plastic. Copper or steel pipes may freeze and thaw faster than PVC or CPVC plastic pipes.

Insulation

Insulated pipes take longer to freeze, but will also thaw more slowly. The insulation acts as a barrier keeping warmth from reaching the frozen pipe.

Water flow

Restored water flow warms pipes faster on the inside. Stagnant water in a fully frozen pipe takes the longest to thaw.

Pipe location

Pipes exposed to warmer interior air thaw faster than those against cold exterior walls. Buried underground pipes thaw slowest in frozen ground.

Expected thawing time by temperature

Here are general estimates for how long frozen pipes may take to thaw at various temperatures:

Temperature Estimated Thawing Time
50°F or higher Within 24 hours
40° – 50°F 24 to 48 hours
30° – 40°F 48 hours to 4 days
20° – 30°F 4 days to over a week
10° – 20°F Over a week to several weeks
Below 10°F Several weeks to months

At above freezing temperatures, a fully frozen pipe may thaw in about a day. Near-freezing temperatures in the 30s can take several days. In very cold wintertime temperatures, thawed pipes may not occur for weeks without intervention.

Thawing frozen pipes safely

While allowing pipes to thaw naturally is an option, it may be faster, safer, and prevent more damage to speed the process along. Here are some safe methods to thaw pipes:

Increase interior heat

Raise the thermostat temperature in areas near frozen pipes to warm the air and radiate more heat. Use space heaters, heat lamps, or hair dryers to directly warm pipes.

Insulate pipes

For exposed pipes, wrap insulation around them to retain heat and prevent refreezing. Foam rubber pipe insulation is ideal for this.

Run warm water

If you have any water flow not frozen, run warm water in other faucets. This takes advantage of recirculating hot water flow that may warm adjacent frozen pipes.

Apply heat tape/cable

Plug in electric heat tape or heat cable wraps along the length of the pipe to safely apply heat and accelerate thawing.

Pour warm water

Hold rags or towels soaked in hot water against frozen sections of pipe to directly introduce heat. Pour warm water on the pipe, catching the draining water in a bucket.

Preventing frozen pipes

It’s much easier to prevent frozen pipes than dealing with the aftermath of thawing them. Here are some prevention tips:

  • Insulate pipes in unheated areas like attics, basements, or garages.
  • Seal leaks and drafts to stop cold air reaching pipes.
  • Wrap outdoor hose bibs and spigots with insulating covers.
  • During cold snaps, let faucets drip slowly to keep water moving.
  • Keep thermostat set to at least 55°F when away during winter.
  • Close garage doors to protect plumbing running through this area.
  • Disconnect and drain outdoor pipes and irrigation systems before first freeze.
  • Consider installing freeze-proof faucets or valves which shut off water automatically if temperatures drop too low.

Conclusion

Allowing frozen pipes to thaw naturally requires patience. At just below freezing temperatures, a couple days may do the trick. But during frigid wintertime cold, full thawing may not occur for weeks without taking active steps to speed the process along safely. Your best bet is to prevent frozen pipes in the first place by eliminating cold drafts near plumbing, maintaining adequate heat, and insulating vulnerable pipes.