Disinfection by-product samples are collected from which part of the water system?

Disinfection by-product samples are collected from the distribution system due to the nature of how these by-products form and are distributed throughout the water supply. In the distribution system, chlorine or other disinfectants are used to treat the water to ensure it is safe for consumption. As water travels through the pipes, it can react with organic matter, leading to the formation of disinfection by-products. This sampling is critical because it allows for the assessment of water quality and compliance with regulatory standards, ensuring that the water reaching consumers meets safety guidelines.

Collection from the distribution system is essential since it reflects the water quality that consumers ultimately receive, including any contaminants or by-products that might be present after the water has undergone treatment and traveled through the infrastructure. Other options, such as point of use sites, customers' plumbing fixtures, and storage reservoirs, do not provide a complete picture of the potential presence of disinfection by-products as they may not accurately represent the water quality throughout the entire distribution network.