Willingness and ability to pay for water&sanitation

In many countries in the world, above all in the periurban and rural areas, the water supply network is not available and sanitation facilities are rare and shared among many households, if existing at all. Paying for water supply and for the provision of sanitation facilities could be the right solution also for developing countries, but how should the charging scheme look like? And how much would be rural and periurban households willing to pay? And wouldn’t the low ability to pay of such households hinder the process of developing a sound WSS network? This video gives a good overview of the water and sanitation supply around Lusaka, Zambia, and illustrates a possible charging option: http://www.youtube.com/watch?v=BJmWN921EtQ I would be really interesting to know what you all think about this topic!