The study suggests that more focus on water storage and hand washing in media campaigns combined with more concerted efforts by the state to provide clean water to slum communities would greatly assist in controlling the incidence of childhood diarrhoea. Epidemics of diarrhoeal diseases and cholera mainly occur twice a year, coinciding with hot and humid summer months and during and after the monsoon floods. The paper identifies the risk and duration of child diarrhoea, its relationship to engineering, behavioural and socio-economic factors, and computes the economic costs to slum households