Abstract: Flow control and fire detection and location apparatus is disclosed. The apparatus is used with a system which circulates heated or cooled water for use in connection with the heating and air conditioning system of a building and to sprinker heads. The apparatus comprises a short length of tubing or pipe connected downstream of a sprinkler connection to provide a bypass for flow of heated or cooled water around a segment of the return line from heating or cooling apparatus to a standpipe through which the water is returned to an equipment room. There are check valves to prevent flow of water through the bypass toward the heating or cooling apparatus, and to prevent water flow in the bypassed segment from the heating or cooling apparatus toward the standpipe. There is also a flow sensor in the bypassed segment. In normal operation, water from the heating or cooling apparatus flows through the bypass line to the standpipe and back to the equipment room for heating or cooling and recirculation.