Denver tap water is generally safe to drink, meeting or surpassing all federal and state water quality standards set by the Environmental Protection Agency (EPA). The utility responsible for the supply conducts rigorous and frequent testing to ensure the water is clean before it enters the distribution system. However, the final quality of the water reaching a home can be affected by the building’s internal plumbing and service line material. This means that while the city’s water supply is safe, localized issues, such as those involving older pipes, can introduce contaminants and require homeowner attention.
The Origin and Protection of Denver’s Water Supply
Denver’s water supply begins as high-altitude snowmelt in the Rocky Mountains. This runoff is collected across an extensive 4,000-square-mile watershed, primarily flowing into the South Platte River and its tributaries, as well as multiple reservoirs like Dillon and Gross. This mountainous origin provides a naturally high-quality source water that requires less intensive treatment compared to supplies drawn from lower-elevation rivers.
Denver Water focuses on watershed protection and management to preserve this source before treatment. The utility actively engages in collaborative forest health programs and wildfire mitigation efforts across the collection area. These proactive measures are designed to protect the watershed from contamination risks like erosion and debris, which could compromise the raw water quality.
Treatment Processes and Regulatory Compliance
Denver Water utilizes a comprehensive, multi-barrier treatment process at its facilities to purify the raw source water. The initial steps involve coagulation and flocculation, where chemicals are introduced to bind microscopic particles and dirt into larger clumps called floc. This is followed by sedimentation, allowing these heavier particles to settle out of the water.
The water then moves through a filtration stage, typically involving layers of anthracite coal and sand, which physically remove suspended matter, bacteria, and parasites. The final step is disinfection, where chlorine or chloramine is added to destroy any remaining disease-causing organisms. This disinfectant residual is maintained throughout the distribution system to protect the water as it travels to homes and businesses.
Compliance is maintained through strict adherence to the federal Safe Drinking Water Act (SDWA), with oversight from both the EPA and the Colorado Department of Public Health and Environment (CDPHE). The utility conducts approximately 145,000 tests annually on water samples taken throughout the system. These results are compiled and published for public review in an annual Consumer Confidence Report.
Addressing Specific Contaminant Concerns and Home Plumbing Risks
Lead Contamination and Mitigation
The most significant contaminant risk to consumers is lead, which leaches from older, customer-owned lead service lines or internal plumbing, not the treated water supply. It is estimated that between 60,000 and 84,000 properties, particularly homes constructed before 1951, may still have these older lines. Denver Water is executing a multi-year Lead Reduction Program that replaces customer-owned lead lines with copper at no direct cost to the property owner. As a temporary measure, the program also provides affected customers with pitcher filters certified to remove lead. Furthermore, the utility utilizes corrosion control by adjusting the water’s pH level to create a protective coating inside existing lead pipes, limiting the metal’s release into the water.
Aesthetic Concerns
Aesthetic concerns, such as a noticeable taste or odor, are often attributed to the use of chloramine as the primary disinfectant. Unlike chlorine, which dissipates quickly, chloramine residuals remain longer in the water, which can produce a medicinal taste for some users. While generally harmless, this taste can be reduced by using a simple carbon filter or by letting the water sit in an open container for a short period.
Emerging Contaminants
Denver Water also proactively monitors for modern concerns like Per- and polyfluoroalkyl substances (PFAS) and microplastics. Testing for PFAS has been underway since 2017, and the treated water consistently shows levels well below the limits established by the EPA’s latest regulations. The utility also monitors research regarding microplastics, ensuring that its extensive filtration systems are prepared to address any regulatory or health-based concerns about emerging contaminants.