Whilst we are on a mains water supply, the provision of clean water has an energy and carbon cost and it makes good sense to reduce our consumption.
That is whay all taps and shower heads in the cottages are 'low-flow' to save water but still run at mains pressure to ensure you'll always get a decent shower! Hot water is constantly circulated through insulated pipes so that you won't need to wait long for it to warm up when you turn the tap on, thus reducing wasted water and energy!
Of course we need to dispose of almost as much water as we use, and in our case this is treated naturally in a septic tank.