UN Independent Expert Catarina de Albuquerque says that the right is not only about sustainable access, but covers affordability, accessibility, acceptability, and quality of sufficient water for basic personal and domestic use. While 20 litres of safe drinking water is considered the basic minimum for survival, 50-100 litres is needed to ensure full realisation of the right.
Catarina de Albuquerque started a three-year assignment in November 2008 as Independent Expert on the issue of human rights obligations related to access to safe drinking water and sanitation. Besides providing policy advice to the UN, she is also preparing a compendium of water and sanitation best practices.
http://www.irc.nl/page/51931