You should start dripping your faucets when outdoor temperatures are at or below freezing for several hours, especially if they’re forecast to dip near or below about 20°F for part of the night.

Quick Scoop

Rule of thumb

  • Start dripping when:
    • The forecast shows temperatures at or below 32°F (0°C) for several hours, especially overnight.
* Or when temps are expected to drop near/below 20°F (-6 to -7°C), which is a common threshold plumbers use for frozen-pipe risk.
  • Turn the drip on before the coldest part of the night (often late night to early morning), not after everything is already frozen.

Key situations to drip

  • When a hard freeze is forecast: temps at or below 20°F for 3+ hours.
  • When pipes run along exterior walls, through unheated basements, crawl spaces, attics, or garages. These areas freeze fastest.
  • If your power goes out during freezing weather and your heating can’t run.
  • If you’ve had frozen or burst pipes in your home before during similar temperatures.

Think of it like this: if your local forecast is warning about a “hard freeze” or pipe-freeze risk, that’s your cue to drip.

Which faucets to drip (and how)

  • Prioritize:
    • Faucets on exterior walls.
    • Faucets farthest from your water meter or main shutoff, so water moves through more of the system.
* Faucets in unheated or drafty areas (garage sinks, laundry rooms, basements).
  • Let both hot and cold side run a little if you can, so both hot and cold lines move.

Drip rate

  • You don’t need a stream; a small, steady drip or tiny trickle is enough:
    • About 1–2 drips per second, or a thin pencil‑lead‑wide stream in very cold weather.

When to stop dripping

  • You can stop once:
    • Temperatures are consistently above freezing (above 32°F) day and night, and
    • There’s no more freeze warning and your pipes show no signs of freezing.

If in doubt, keep dripping through the coldest night in the forecast; a little water use is cheaper than a burst pipe repair.

TL;DR: Start dripping before a hard freeze—typically when temps are predicted to fall to around 20°F or below for several hours, especially overnight, and focus on faucets on exterior or unheated lines.