Bill Houghton, Sebastopol, CA
We do get frost - "sunny California", where it never freezes, is down south (although the passes north of Los Angeles got nailed today, major snowstorm, snow down to 2,500 feet, chains, etc.). But I'm not sure we even really have a frost line.

Local code requires water pipe be buried 12" below finished grade; that and getting under the foundation will be the controlling factors, if we do have to replace it.