United Nations -- Data on the water and sanitation indicators related to the Millennium Development Goals is available at http://unstats.un.org/unsd/mi/mi_goals.asp .
World Bank -- The World Bank provides water and sanitation data in time series on its World Development Indicators data base.
World Resources Institute (WRI) -- WRI provides both data and GIS shapefiles related to Water Issues. WRI provides these links to water related and other data at https://www.wri.org/resources/data-platforms .and water related and other data at https://www.wri.org/resources/data-sets
DHS Program-- The DHS program carries out regular demographic and health surveys in a number of developing countries. Data and shapefiles at the national and sub-national level on water and sanitation are available at https://www.statcompiler.com/en/.