The City of Hayward has a cross-connection control program to protect the City's drinking water distribution system from contamination caused by backflow. Under normal conditions, water from the distribution system flows into a consumer's premises. When backflow occurs, water from the consumer's premises flows into the distribution system. If that water is contaminated because of activities on the consumer's premises (for example, addition of rust-inhibiting chemicals to a boiler or use of photo-processing chemicals), the water can carry contaminants into the distribution system, possibly causing illness or even death.