Frankly, it is not advisable to conserve water by allotting only 12 hours a day with water. People--rich and poor alike--will simply buy huge plastic tubs and drums and fill them up with water to stock up and compensate for the 12 other hours without water, most of which will spill over and get wasted in the process.

Water conservation is a matter of personal discipline. Unless someone wants to boost the sales of plastic tubs and drums.