A supply line freezes where cold air reaches it: exterior walls, crawl-space runs, garage ceilings, and the cabinet under a sink on an outside wall. A drain or lateral freezes differently - where water stands in a belly and the frost line finds it. Eau Claire's frost depth makes both plausible in a hard January.
Act in this order: warm the space (open cabinets, raise the room heat), find and be ready at the shutoff for that branch, and get a thawing call placed early in a snap - crews queue fast. Never use open flame; the fire statistics on that are unambiguous.
After the thaw, the split check matters as much as the thaw: many frozen lines have already burst and only announce it when water flows again. The permanent fix is air sealing and insulation at the cold path, or a heat cable on the repeat offender - not luck.
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