Freeze protection device

In a water supply system for a building wherein water is supplied to the building from a water main through a buried pipe, a protective system comprising:

• valve means in the buried pipe shiftable from a first position in which it permits flow of water from the main into the building to a second position in which it shuts off flow of water from the main and allows water to drain out of the building through the buried pipe;
• temperature-responsive means arranged to control the valve means and to shift the valve means to its second position when the temperature sensed by the temperature-responsive means falls below a first predetermined level;
• electrical heat trace means located in proximity to said temperature-responsive means to maintain the temperature-responsive means at a temperature above said first predetermined level when energized;
• at least one temperature-responsive drain means within the building, for draining at least part of the water system within the building when the temperature within the building falls below a second predetermined level;
• first thermostat means responsive to outdoor ambient temperature;
• second thermostat means responsive to temperature within the building;
• and
• means connecting the first and second thermostat means to control energization of the heat trace means so that the heat trace means is energized when the outdoor ambient temperature is below a third predetermined level and the temperature within the building is above a fourth predetermined level and so that the heat trace means is otherwise deenergized.