Separation of yellow waste water and rainwater, and their subsequent use in agriculture (yellow water) and residential (rainwater) is real. When using tank rainwater, tanks to stabilize urine and domestic wastewater treatment plant we will have 85% savings in potable water.

The article deals with the influence of the floor area of house energy supplied to the hot water. Mutually compare three methods of calculation and one of them use in the calculation of delivered energy for hot water system, through which energy class is designed for local consumption - the warm water.