The general rule is to let faucets drip when outdoor temps are around 20°F (-6°C) or lower, especially for pipes in unheated or exterior-wall areas. You do not need to run water constantly whenever it is just below 32°F if your pipes are well insulated and your home is kept warm.
When to start dripping
For most homes, the “danger zone” for freezing pipes is when:
- Forecast lows are near or below 20°F for several hours overnight.
- Pipes run through unheated spaces (crawl space, attic, garage, unheated basement) or along exterior walls.
Start a drip before temperatures actually reach their lowest point (usually late night to early morning) and keep it going through the coldest hours.
Which faucets to run
Focus on the most vulnerable lines, not every faucet in the house.
- Let a farthest-away faucet from the main, especially on an exterior wall, drip cold water in a thin stream (slightly more than a drip is ideal).
- If you know specific sinks sit on exterior walls or in very cold rooms, drip those as well and open the cabinet doors under them so warm air reaches the pipes.
How much water to run
You only need a small but steady flow.
- Aim for a slow drip or tiny stream, often described as no wider than a pencil lead; a full flow is unnecessary and wastes water.
- The goal is to keep water moving, since flowing water is much less likely to freeze than stagnant water in a cold pipe.
If you share your typical winter lows, house age, and where your plumbing runs (exterior walls vs interior), more tailored guidance is possible.
