water distribution in housing

In order to have a hot-water-bath in the house, the cold water from the mains need to be collected in the cold water tank which is located in the roof part of the house. In this process, cold water will pass a pipe which start from mains and end in the cold water tank. While the cold water is flowing through the pipe into its tank, it can also be flown through many other cold water pipes which output in the sink, bath, wash basin, or toilet in the house. After it reach the cold water tank, some part of this cold water will be flown and collected in the hot water tank in the second floor of the house. At there, the cold water will be heated into hot water. The hot water which come out from there will be distributed through the hot water pipes into the sink, bath, or wash basin in the entire house.