A heated, insulated cover for a portion of a pipeline with valve and backflow preventer components exposed to the atmosphere, the cover being sectionalized so as to be asemblable around the valve components, with hand manipulated clamps to hold the cover together, an electric heating element inside the cover to keep it above freezing temperature, drain openings in the cover at ground level to let any water drain out of the cover, doors in the cover to permit inspection and testing of the components when the cover is in place.