Castle Rock water system nears completion of maintenance, returns to chloramine in May

Castle Rock Water is preparing to return its system to chloramine between May 11 and May 18 after a months-long free-chlorine maintenance cycle that began Feb. 2. For most households and businesses in Castle Rock, the main change should be behind the scenes: crews will flush hydrants across town, while the water is expected to remain safe for drinking, cooking and cleaning.

Town officials said residents are not expected to notice a change in taste or odor during the transition back. The latest alert from the Town of Castle Rock said the maintenance activity was nearly complete, and the utility stressed that the disinfectant switch is being handled on a set timetable rather than in response to a contamination event or emergency.

Castle Rock Water said the temporary free-chlorine step was started after routine water-quality testing identified potential biofilm buildup in the distribution system. The town said all drinking-water systems naturally develop biofilm inside pipes and storage tanks, and that the cleaning work was meant to reduce that buildup and protect disinfectant effectiveness as the system moved through the spring and early summer irrigation season. The utility also said this was the first time it had carried out this full procedure.

During the maintenance period, the town said chlorine levels stayed below the State and Federal maximum of 4.0 parts per million. Castle Rock Water said the Colorado Department of Public Health and Environment reviewed and supported the work and received the town’s increased sampling data. The town also said water remained safe for drinking, bathing, cooking and other household uses throughout the maintenance period.

For customers with sensitive water uses, the town has pointed to a few specific concerns. Castle Rock Water said some residents with home dialysis, aquariums or production uses such as breweries may need proper chlorine filtration. Customers who want to remove chlorine for aesthetic reasons can let water sit in an open pitcher for 24 hours or use a carbon filter designed for chlorine removal.

The return to chloramine marks a shift back to the disinfectant Castle Rock has used since 2013. Chloramine is the routine municipal disinfectant in the system, and the town said the cleanup was a standard step meant to keep the network operating as intended. As the switch back begins, the practical message for Castle Rock is simple: hydrants will be flushed, routine water use can continue, and the system is moving back to normal operations in mid-May.