Modern societies are, by definition, made up of complex and interlinked systems of people, laws, political and financial institutions, private companies, technologies, markets all constantly interacting, both formally and informally and responding to different sets of incentives, sanctions and influences. This is how they work, and this is how they provide services to their citizens. This is as true for the water and sanitation “sector” and the services they deliver as any other part of a modern economy. A starting premise for taking a systems approach is the understanding that any given WASH System is a complex adaptive system. Adopting a “systems approach” therefore means recognizing and understanding that any strong national system for WASH service delivery will require all of the elements (factors to be in place and at all institutional levels and include different actors – from households and communities to local government and national ministries to private companies and aid agencies to politicians – being able to work together effectively and at scale.