Hose bibs are the number one failure
Disconnect every garden hose before the first cold night. A hose left attached traps water in the bib, and that trapped water is what expands and cracks the valve body.
Once the hose is off, a foam bib cover from any hardware store is a few dollars and does the rest. If you have an older non frost free bib on a north facing wall, the cover matters more.
Garage and exterior wall runs
Water heaters and laundry lines in an uninsulated garage are the next most common split we see. Foam pipe sleeve on any copper you can reach handles it, and it takes one afternoon.
If a pipe runs along the outside of the house to a back yard sink or pool equipment, sleeve that too, or shut its isolation valve and drain it for the season.
If a pipe already froze
Do not use a torch or open flame. Open the nearest faucet so melting water has somewhere to go, then warm the pipe slowly with a hair dryer working from the faucet back toward the frozen section.
If no water comes through after warming, or you hear water running with every tap closed, shut the main off and call. A split that is still frozen has not started leaking yet, and that is the cheap moment to fix it.
Need a hand with this? See our emergency plumbing repair page, or call 626-386-9105.