In the 30 years that Josephine Muthoni has lived in Nairobi's Mukuru slum, she has never had a steady supply of clean water.

The only way to get water was from vendors dotted around the slum, who charge exorbitant prices for the often polluted water they buy from government water points or steal straight from the municipal pipes, the 62-year-old mother of nine explained.

Muthoni said filling a 20-liter (5-gallon) jerry can cost as much as 50 Kenyan shillings ($0.45) — a potentially crippling amount in a city where the majority of slum dwellers earn less than $1.90 a day, according to the World Bank.