Example: a bathroom line freezes in an outside wall and splits on the thaw

The situation

Illustrative example. Not a real job or customer.

In this invented example, a single-story brick ranch built in the 1950s has its only full bathroom on a north-facing exterior wall. During a several-day cold snap, the owners wake to find no water at the bathroom sink, though the kitchen works. They open the vanity doors and set a small space heater in the bathroom. Around midday the sink starts running again, and twenty minutes later the hallway carpet outside the bathroom is wet.

1. One owner closes the main shutoff in the basement utility area, which they had located the previous fall.
2. They switch off the space heater and the bathroom circuit because water is spreading toward an outlet near the floor.
3. They take photos of the vanity, the wet floor and the hallway carpet, then pull the carpet back from the tack strip to see how far the pad is wet.
4. A plumber finds a split in the copper line inside the wall behind the vanity and replaces the section, opening a small square of drywall to reach it.
5. Moisture readings show wet drywall at the base of the bathroom and hall walls, a wet bottom plate and soaked carpet pad in the hall. The basement ceiling below the bathroom reads damp along one joist bay.
6. Pad is removed, carpet is lifted and dried, and drying equipment runs in the bathroom, hall and basement for several days with daily readings.

Because the water was clean and was shut off within minutes, most of the drywall and the carpet itself could be dried. The pad, a section of baseboard and the drywall the plumber had opened were replaced, and the exterior wall was insulated better while it was open.