It appears that one key issue is always missing from these types of proposals and that is "Plumbing and Building Regulations".
Tremendous household and office waste water occurs, firstly by running clean water from the hot tap until water of the desired temperature is obtained and secondly, with rinsing when the water is hardly contaminated.
Roof run off is also either not collected or overfills any water butts and goes to ground or sewer.
The use of taps rather than either foot controls or infra red switches to switch off running water immediately it is not needed is wasteful.
Solutions are likely to involve low head pumping, large storage tanks and changes to the building regulations to enforce some of these changes. Obviously there would be a cost, but is there also a cost benefit, particularly if installed in new houses?
Perhaps one of the specialist water engineers could advise what action is or has been taken to make more use of these wasted resources.
DAVID GARDNER (F), Exton, Devon, firstname.lastname@example.org