Rowlett Water Hardness & Quality Report (2026)

Rowlett, Texas, in Rockwall County on the east shore of Lake Ray Hubbard — a growing Dallas suburb on the reservoir just east of Garland, known for its waterfront community and rapid residential growth — draws its municipal water supply from Lake Ray Hubbard (East Fork Trinity River) via the City of Rowlett Public Works Water Division, treating Trinity River watershed water for Rowlett. Water hardness in Rowlett measures 110.5 mg/L — classified as moderately hard.

Rowlett's moderate hardness — notably softer than many Dallas-area communities (Moore, OK area: 351 mg/L; Richardson-area supplies: 200+ mg/L) — reflects Lake Ray Hubbard's moderate calcareous watershed input. Lake Ray Hubbard on the East Fork Trinity River drains the East Cross Timbers (Upper Cretaceous Austin Chalk — calcareous chalk, but with moderate dissolution rates; Eagle Ford Shale — calcareous marine shale); the Blackland Prairie (Taylor Marl and Navarro Group — calcareous Cretaceous clay and marl); and the Pennsylvanian calcareous sandstone and shale of the East Texas basin in the upper watershed. The Lake Ray Hubbard reservoir dilutes the watershed's calcareous input, producing the moderate 110.5 mg/L at Rowlett — softer than Trinity River supplies downstream that accumulate additional calcareous dissolution.

At 110.5 mg/L, Rowlett residents encounter moderate scale accumulation. Faucet aerators and showerheads develop deposits after several months — monthly cleaning with citric acid solution is practical maintenance. City of Rowlett Public Works Water Division consistently delivers water meeting all Texas TCEQ and EPA Safe Drinking Water Act requirements.