Operational definition of terms Control arm: Group of clusters provided with no household water treating product and allowed to continue with their customary practices. Effect: The influence of treating drinking water with a water treatment product on the incidence of diarrhea in under-five children. Household water treatment with chlorine: Treatment of drinking water using bleach (sodium hypochlorite) at the household level. Improved drinking water: Drinking water obtained from a pipe, public tap, borehole, protected spring, protected dug well, or rainwater. Intervention arm: Group of clusters provided with point-of-use water treatment product to treat their drinking water. Point-of-use water treatment: Treatment of drinking water for household use at the point-of-use.