How deep do you have to bury a water line so it does not freeze?

To keep a water line from freezing, it needs to be buried below the frost line.The frost line is the depth below the surface of the ground at which the water in soil is expected to freeze.

The depth of the frost line varies depending on how severe the winter season in a given area typically is. The Adirondack Almanac provides a map of the average frost line depth for most of the United States. When a water line has not been buried deep enough, or when winter ends up being colder than usual, certain measures, such as keeping the basement of a house warm or leaving the water in the line on a trickle, can be taken to reduce the likelihood of a freeze.