You generally only need to run (drip) water when temperatures are well below freezing for several hours and your pipes are in cold or exposed areas. A good rule of thumb many plumbers use is to start dripping faucets when outdoor temperatures are expected to drop to around 20°F −6.6°C-6.6°C−6.6°C or lower, especially overnight or during long cold snaps.

Key temperature guidelines

  • Start thinking about protection (insulation, opening cabinets, heat on) any time temps dip below 32°F \0°C\ for more than a few hours.
  • Actually run a slow drip when:
    • The forecast is for about 20°F −6.6°C-6.6°C−6.6°C or colder.
    • It will stay below freezing for many hours (especially overnight).
    • Your plumbing is in unheated or poorly insulated spaces (crawl spaces, exterior walls, garages, basements, attics).

Which faucets to run

Focus on lines most likely to freeze.

  • Faucets on exterior walls (kitchen sinks on outside walls are common trouble spots).
  • Fixtures above unheated areas (over garages, crawl spaces, basements).
  • The faucet farthest from the main shutoff, because moving water through the whole run helps protect more of the system.

Let them run at just a thin stream or fast drip—more than a drip, but less than a steady pencil-thick stream—to keep water moving without wasting too much.

How long to keep water running

  • Turn the drip on before temperatures drop below freezing, usually in the evening before the coldest part of the night.
  • Leave faucets dripping until outdoor temperatures are consistently above 32°F \0°C\ during both day and night or the cold snap passes.
  • If you’re leaving town during a hard freeze, many local utilities recommend:
    • Keeping your heat at about 55°F \13°C\ or higher.
    • Shutting off the main and draining lines if possible, or leaving a drip plus heat on if you can’t drain.

Extra steps beyond running water

Running water is just one layer of protection and shouldn’t replace basic winter prep.

  • Keep your thermostat at least around 55°F during cold weather, even at night or when away.
  • Open cabinet doors under sinks on exterior walls so warm air can reach the pipes.
  • Insulate exposed pipes in unheated areas (crawl spaces, attics, garages, basements).
  • Disconnect and drain outdoor hoses and use insulated covers on outdoor spigots.

Quick SEO-style notes (for “when should I run water to keep pipes from

freezing”)

  • This topic shows up a lot in winter forum discussion and local city advisories when a cold snap or “polar vortex” is in the latest news, especially in areas not used to deep freezes.
  • Many community posts say they begin to drip pipes when forecasts show low 20s°F and they won’t be awake or home to react if temps drop more than expected.

Bottom line: run a light stream from at-risk faucets when temps are forecast near or below 20°F for several hours, especially overnight or during prolonged freezes, and keep doing it until the cold spell breaks.

TL;DR: Start a slow drip from vulnerable faucets when temperatures are headed toward the low 20s°F or colder, during long or overnight freezes, and keep them dripping until it’s safely above freezing again and your home is warm and insulated.

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