When talking about saving energy for building, hotel… most of us will think about the system which consume a lot of energy like HVAC system or Lighting system … but almost forgot that plumbing system also consumes a considerable amount of energy too.
There were many solutions for saving water like change old genration valve/shower system (consuming flow about 2.642gallon/min) to the newer generation (which using mechanism that mix small air bubbles into water and make user still feel fully water impulsiveness) that saving 35% amount of water; or change the toilet has flush tank(cap. 3.17 gallon/min) to water-efficient toilet that help reduce the noise and save 20% amount of water.
Moreover, one of saving water solutions is recycling water or utilizing rainwater.
The diagram below show a solution that use underground rainwater storage tank for toilet, unrinal and watering plants.