Lewisville Water Hardness & Quality Report (2026)

Lewisville, Texas — a major Dallas suburb in Denton County — draws its municipal water supply from Lake Lewisville on the Elm Fork Trinity River in Denton County, sourced through the City of Lewisville Water Utilities and the Upper Trinity Regional Water District (UTRWD) regional pipeline infrastructure. Lake Lewisville is the same East and Elm Fork Trinity Blackland Prairie reservoir serving Carrollton (318 mg/L) and other DFW Metroplex cities. Water hardness in Lewisville measures 99.5 mg/L — classified as moderately soft, significantly lower than other Lake Lewisville-dependent cities.

Lewisville's surprisingly lower hardness compared to Carrollton and Denton (both drawing from the same reservoir system) suggests a significantly different treatment and blending approach at the Lewisville Water Utilities treatment plant. While Lake Lewisville source water reflects the same Cretaceous Austin Chalk and Taylor Marl Blackland Prairie carbonate geology as the rest of the Elm Fork Trinity watershed, Lewisville's water treatment process likely includes lime softening or ion exchange as part of the treatment train, or the city blends Lake Lewisville water with softer groundwater or imported supplies at a higher ratio than neighboring cities. The treated finished water hardness of 99.5 mg/L is dramatically lower than the raw source would suggest.

With hardness at 99.5 mg/L, Lewisville residents experience moderate scale accumulation over time. Faucet aerators and showerheads develop deposits after several months — monthly cleaning with citric acid solution is standard maintenance. Dishwashers produce clean glassware with moderate rinse-aid use. City of Lewisville Water Utilities consistently delivers water meeting all Texas TCEQ and EPA Safe Drinking Water Act requirements.