When temperatures drop into the low 20s and teens.
If you have a Bibb Shutoff – Some homes have an indoor “Hose Bibb” shutoff valve, often in the front hall closet, for the outside faucets. Open the outside water faucet(s) and then turn off the inside Bibb valve. The off position: valve is perpendicular to the pipe. Opening the outside faucet(s) first, allows the pipe to drain after you have turned off the Bib Valve.
If you don’t have a Bib Shutoff (or as added protection) – Purchase an inexpensive cover for your outside faucets from a local hardware store.
Bathroom Sinks – Open cabinet doors under sinks and allow faucets to drip until the outside temperature rises to at least 30 degrees.