A simulation framework is proposed to design disinfectant residual maintenance and early warning monitoring systems against pathogenic contaminations in drinking water distribution systems. In particular, it is investigated how residual maintenance can be tailored keeping into account the presence of a warning system and vice-versa. A multi-species network water quality model that includes disinfectant decay and disinfection kinetics quantifies the risk of delivering contaminated water to consumers. The early warning monitoring system is designed to further minimize consumer exposure using a mixed-integer linear programming problem. For an assumed set of contamination events, system vulnerability is quantified as the cumulative distribution function of the number of consumers that are affected by the contaminations before the warning system raises an alarm. Design and effectiveness of these consumer protection measures are discussed.