What floor does the secondary water supply for high-rise buildings start from? Do you know

Generally, the secondary water supply of high floors starts from the seventh floor, and the pressure of municipal drainage pipe network can only be guaranteed to be used below the sixth floor. Once it is higher than the 6 th and 7 th floors, it is necessary to carry out secondary pressurized water supply. In fact, with the technical progress of housing construction, the proportion of high-rise residential buildings is rising, so secondary water supply is widely used in your high-rise residential areas now.