A customer calls in reporting their water "doesn't smell like chlorine anymore." Is that a real water quality problem, a normal seasonal variation, or nothing at all? Knowing how to answer that question with a field test instead of a guess -- and understanding why your system's disinfectant behaves the way it does between the plant and the tap -- is what separates process-control-level distribution work from entry-level tasks.
Chlorine vs. Chloramine: Different Residuals, Different Behavior
Most Colorado systems disinfect with either free chlorine (hypochlorite or gas chlorine, unreacted with ammonia) or chloramine (chlorine reacted with ammonia, typically monochloramine). The two residuals behave very differently once they leave the plant, and a distribution operator needs to recognize which one their system runs and what that implies:
Free chlorine: