Indoor grey water purification and reuse device, system and method for public buildings

An indoor grey water purification and reuse system for multistory public buildings, comprising:

• a grey water collecting system including fluid conduits fluidically connected to at least one source of grey water for collecting and flowing collected grey water from an upper floor to a floor sequentially below;
• a grey water storage tank (1) located on the floor sequentially below, having an inlet for receiving grey water from a discharge end of the fluid conduits of the grey water collecting system on the upper floor by gravity, and an outlet permitting egress of collected grey water;
• a grey water treatment assembly (2) on a lower floor, sequentially below the grey water storage tank, in fluid communication with the outlet of the grey water storage tank (1), and including at least two purification treatment stages capable of purifying grey water to produce reclaimed water;
• and
• a pressurizable, pneumatic reclaimed water tank assembly (3) for receiving the reclaimed water, including means for disinfecting the reclaimed water, and being capable of supplying the reclaimed water to water to water reuse facilities which are located on the same floor that the pressurizable, pneumatic reclaimed water tank assembly (3) is located, at constant pressure.