The invention relates to a fluid flow monitor and control system which prevents excessive fluid loss and property damage. The invention warns of impending distribution pipe freeze conditions, or ruptures from other causes, shuts off the fluid supply, and vents and drains the piping network under freeze and rupture conditions. Furthermore, the invention shuts off fluid flow if the volume of flow or the velocity exceeds desired norms. An example of its application is as a water main shut-off for residential houses and commercial buildings, it also can be used for industrial processing applications.