Castle Rock Water to temporarily switch disinfectant for system cleaning; officials say water will remain safe

Castle Rock Water staff told the Town Council they will temporarily switch the town’s distribution system from chloramines to free chlorine for about 60–90 days to perform a system‑wide flushing and cleaning procedure expected to begin in January.

Mark Marlowe, speaking for Castle Rock Water, said the program involves a detailed flushing and sampling plan that must be approved by the Colorado Department of Public Health and Environment. He warned residents the change could cause a different taste, odor or slight color in the water for the first few days but emphasized the water will remain safe: “The water is perfectly safe, and this is nothing to be concerned about, but people will notice a difference.”

Staff explained the project will include targeted outreach: notices on the town website and water bills, social media updates, posted notices at the bulk water station, and direct letters and phone calls to facilities that routinely remove disinfectants (dialysis centers, health care facilities, breweries, coffee roasters and pet stores). The department said it plans to stage the conversion so freezing‑weather impacts (icing on roads) are mitigated during winter flushing.

Marlowe said the town converted to chloramines in 2013 and that such temporary conversions may be needed roughly every five to 10 years depending on system conditions such as temperature and water age in storage tanks. Councilmembers asked about frequency and expressed appreciation for the outreach plans. Staff said they expect to receive some customer calls during the change and are preparing scripts and fact sheets for customer service.

Next steps: staff will finalize the flushing and sampling plans and seek CDPHE approval before converting in January; the town will run the conversion for the 60–90 day window and then return to chloramines before irrigation season.