Abstract: A method and apparatus for maintaining a narrow thermocline in a thermal energy liquid storage tank in a cooling system for a commercial building in which the tank provides cooling liquid, e.g., water, during a peak electricity demand period to allow the building system to reduce its electric demand during such period. The tank incorporates a water distribution system including a generally centrally positioned, vertically oriented pipe extending from a bottom of the tank to about a top of the tank. A flange is positioned about mid-way of the pipe for separating an upper section of the pipe from a lower section. A water return line is coupled to the pipe above the flange and a water extraction line is connected to the pipe below the flange. A plurality of circumferentially spaced cool water conduits are connected to the pipe generally adjacent the bottom of the tank and a plurality of circumferentially spaced warm water conduits are connected to the pipe generally adjacent the top of the tank.