Water+systems

=Plumbing=

Dual Toilet-sink
Energy efficient, saves water and also encourages hygenic handwashing. This is only one of many different designs. Water could also be siphoned from the normal and seperate sink and fill a larger toilet basin. This model specifically uses 1.28/0.8 gallons per full/half flush http://www.ebuild.com/articles/999523.hwx

=Water Heating / Thermal Storage= =Water Cooling?=