Thornton, Colorado’s Home for Water Softeners, Water Filters,
& Water Delivery

Yes. Thornton’s drinking water meets federal and state drinking water standards. The city completes required testing for regulated contaminants, and results are reviewed to confirm compliance with Safe Drinking Water Act requirements.

Yes. Thornton’s tap water is considered hard to very hard, depending on location and time of year. In 2024, water hardness ranged from 116 mg/L to 288 mg/L, with an average of approximately 183 mg/L, or about 10.7 grains per gallon. Hard water can contribute to scale buildup on plumbing, fixtures, and appliances, although it is not harmful to health.

Recent sampling for Thornton, Colorado drinking water detected the presence of PFAS chemicals. The EPA is in the process of setting new maximum contaminant levels (MCLs), which range from 4 to 10 parts per trillion, equal to 0.00000000004 for PFOA and PFOS individually, and up to 0.0000000001 for PFNA, PFHxS, and HFPO-DA (GenX Chemicals). As you can see in the water quality report, many samples do not meet these standards. Click here to learn more about our whole house PFAS filtration systems.

Yes. Fluoride was detected in Thornton’s drinking water at levels ranging from 0.5 to 0.8 ppm, which is below the EPA maximum contaminant level of 4.0 ppm. Fluoride occurs naturally from erosion of mineral deposits. Thornton does not add fluoride as part of its treatment process.

Thornton’s water supply comes from a diversified portfolio of water rights in the South Platte River, Clear Creek, and Cache la Poudre River watersheds. South Platte water is diverted north of Denver and stored in reservoirs before treatment. Clear Creek water is primarily stored in Standley Lake, with a smaller portion stored locally in Thornton reservoirs. Water from the Cache la Poudre River is transported via irrigation ditches to reservoirs near Fort Collins and then pumped through a 70-mile pipeline to Thornton’s treatment plants.

Thornton treats its drinking water at multiple treatment plants using multi-step processes that include coagulation, filtration, disinfection, and turbidity control. Water quality is monitored continuously from raw source water through treatment and distribution to customer taps. Thousands of laboratory analyses are performed annually to ensure water remains safe and compliant with all regulations.

While Thornton’s water meets all safety standards, many homeowners choose additional treatment to address hardness, scale buildup, taste, or trace contaminants. A water softener can help reduce calcium and magnesium minerals that cause scale, while filtration systems may improve drinking water taste and clarity at the tap.

Thornton operates a robust monitoring program that includes tens of thousands of water quality samples each year. Testing is performed by the city’s Water Quality Laboratory and includes regulated and unregulated contaminants, microbiological testing, and PFAS analysis.

Residents can review Thornton’s most recent Annual Water Quality Report here.