Chlorine residual is one of the most closely monitored parameters in any drinking water distribution system.
But what if a quicker than normal decline in residual is a symptom rather than the problem itself?
EPA guidance notes that biofilms and sediments on piping and tank surfaces can harbor microorganisms that consume disinfectant.
So when disinfectant demand increases, the better question may not be:
“Do we need to add more chlorine?”
It may be:
“What can we remove that is consuming it?”
Managing drinking water quality ultimately means managing the infrastructure that stores and delivers it.
Useful EPA reference, including the section "Keep the Distribution System Clean":