What typically causes cross-connections in water supply systems?

Cross-connections in water supply systems occur when there is a physical connection between a potable water supply and a source of contamination. The primary cause of these cross-connections is backflow and backsiphonage of contaminated liquids.

Backflow happens when the normal flow of water is reversed, allowing non-potable water or contaminants to flow back into the clean water supply. Backsiphonage is a specific type of backflow that occurs due to a pressure drop in the water supply, creating a vacuum that draws water from a connected source. This situation can lead to serious health risks if the contaminants from the non-potable source enter the drinking water supply, which is why preventing cross-connections is critical in water system management.

While improper sewage disposal methods and excessive water pressure can create other issues in water treatment, they are not direct causes of cross-connections. Additives in water treatment can contribute to water quality but do not inherently cause physical connections to occur that would lead to contamination. Thus, backflow and backsiphonage provide the specific mechanism under which cross-connections can develop, making it essential knowledge for ensuring safe drinking water and protecting public health.