Abstract: The present invention describes a method, system and apparatus for optimizing a flow of thermal fluid through one in a multitude of local reservoirs (e.g. water tank) which may have local heating capability and which shares a common water heating source (e.g. solar panels). Keeping a minimal flow from the inlet to the outlet allows a continuous temperature difference monitoring, which is then used to vary the local flow through an automated system, while also taking in consideration the effect of an optional local heating source. The said above may be applied in reverse for cooling systems.