Castle Rock water utility to temporarily switch disinfectant for system flushing; officials promise outreach

Mark Marlowe, a Castle Rock Water official, told the Town Council the utility will temporarily convert from chloramines to free chlorine for roughly 60–90 days to perform a system-wide flushing and “spring cleaning.” He said the work will require detailed flushing and sampling plans that must be approved by the Colorado Department of Public Health and Environment and will start in January.

"The water is perfectly safe, and this is nothing to be concerned about," Marlowe said, adding that residents may notice a change in taste, smell or slight color for the first few days. He said the utility is preparing targeted outreach — including letters and phone calls to dialysis centers, health-care facilities, breweries, coffee roasters and pet stores — and broader notifications through bills, web postings and social media.

Marlowe said no new equipment is required; crews will switch disinfectants, run the system for the 60–90 day period, then convert back before irrigation season. In response to a council question about frequency, he said the conversion is not annual and may occur every five to 10 years depending on water age, temperature and system conditions.

Councilmembers were briefed on the operational steps, the need to manage flushing in winter (to avoid icing on roads), and the likely customer calls the town will receive. Staff committed to issuing fact sheets and running a public information campaign ahead of the conversion.