how fast do pipes freeze

Pipes can start to freeze in about 4–8 hours of sub-freezing temperatures, but the exact timing depends heavily on how cold it is, where the pipe is, and how well it’s protected.

Typical freeze timelines

• Around 32°F (0°C): Unprotected pipes generally need many hours (often 10–12+ hours) of continuous cold before they freeze solid.

• Around 25°F (about −4°C): Exterior or uninsulated pipes can start freezing in roughly 4–6 hours, sometimes faster in drafts.

• Around 20°F (about −7°C) or colder: Pipes in unheated or poorly insulated areas may freeze in as little as 3–6 hours.

• Extreme cold plus wind/drafts: Strong drafts around an uninsulated pipe can cut the safe time window in half, down to roughly 2–3 hours in some scenarios.

What affects how fast pipes freeze?

• Temperature and duration : The lower the temperature and the longer it stays low, the faster water in the pipe can reach 32°F and start freezing.

• Pipe location:
  • Exposed outdoor or crawl-space pipes freeze fastest.
  • Pipes in exterior walls are next.
  • Interior pipes, away from outside walls, take the longest to freeze.

• Insulation: Well-insulated pipes stay above freezing longer; bare metal in a draft can freeze quickly.

• Pipe material: Metal (copper, steel) conducts heat out faster than plastic (PEX, PVC), so metal tends to freeze sooner.

• Water movement: A slow trickle through the pipe makes freezing much less likely, because moving water is harder to freeze than still water.

Simple mental rule of thumb

• If it’s below 20°F outside and your pipes are in a cold, unheated space, assume they could start freezing in about 3–6 hours.
• In more moderate cold (25–32°F) with some insulation and indoor heat, you usually have longer, but they can still freeze overnight if conditions are bad enough.

Quick prevention checklist

• Keep the thermostat on and avoid dropping it too low during cold snaps.

• Open cabinet doors under sinks on exterior walls so warm air can reach the pipes.

• Let taps drip very slightly in the coldest spots; even a slow drip can relieve pressure and help prevent a freeze.

• Insulate exposed pipes in basements, garages, crawl spaces, and exterior walls.

• If you’ll be away during a hard freeze, keep the heat on and consider shutting off and draining vulnerable exterior lines.

If you tell me your approximate temperature, how exposed the pipes are (outdoor, crawl space, exterior wall, interior), and whether they’re insulated, I can give a more tailored time estimate for how fast your pipes might freeze in your situation.

Information gathered from public forums or data available on the internet and portrayed here.