Austin Water Hardness & Quality Report (2026)

Austin Water serves the City of Austin and parts of Travis, Williamson, and Hays counties in central Texas, supplying over 100 million gallons daily to more than 1 million residents. Primary sources include surface water from the Colorado River impounded in Highland Lakes reservoirs—Lake Travis (treated at the Wanah Lake Water Treatment Plant) and Lake Austin (treated at the Ullrich Water Treatment Plant)—supplemented by groundwater from the Edwards Aquifer via the Davis Spring wellfield. Major treatment facilities include the 300 MGD R. P. Ullrich Plant and the 165 MGD Tom L. Miller Plant, employing advanced filtration and disinfection processes.

The Colorado River watershed spans the Edwards Plateau, a rugged limestone region of Texas Hill Country where rainwater infiltrates karst aquifers and flows through fractures in Cretaceous-age carbonate rocks. The Edwards Aquifer, a major karst system formed from Edwards Group limestones and dolomites, yields groundwater enriched by dissolution of these formations. Surface water from the Highland Lakes picks up ions from the same geologic strata during basin runoff and reservoir storage, producing a hard supply characterized by significant dissolved calcium and magnesium.

Hard water in Austin drives scale buildup in pipes, heaters, and fixtures, with water heaters most affected—mineral deposits insulate heating elements, raising energy use by 20–30%. Dishwashers, washing machines, and coffee makers are also vulnerable to limescale clogging valves and nozzles. Regular vinegar descaling, sediment pre-filters, and biannual water heater flushing are recommended. A water softener is advised to exchange calcium and magnesium ions, prevent scale, and improve soap efficiency. Austin Water reports average pH around 7.5–8.0, meets EPA lead/copper rules, and shows no detectable PFAS above advisory levels; treatment includes ozonation, chloramination, and UV disinfection per the annual Consumer Confidence Report.