Updated November 1, 2026

Austin tap water: a lake-fed system, and how it has been hardened

Everything that comes out of an Austin Water tap starts as Lower Colorado River water held in Lake Travis and Lake Austin. A single river source keeps things simple, but it also means the utility spends much of its effort protecting those two lakes and the plants that draw from them.

From the river to your glass

Austin Water treats lake water at three plants: Handcox, Davis and Ullrich. The Texas Commission on Environmental Quality has assessed the source and found some intakes susceptible to certain contaminants. That finding sets how often the utility has to sample. Treatment includes lime softening, which lowers hardness and leaves a thin mineral coating that helps keep pipes from corroding. Chloramine is the disinfectant carried through the mains. In 2025, distribution samples ranged from 0.06 to 3.1 ppm and averaged 2.3 ppm.

A timeline of the lake and the plants

• 1950s: lead is no longer allowed in Austin's public pipe network.
• 1960s onward: leftover lead lines are removed during routine maintenance and main rehabilitation.
• February 2, 1973: fluoridation begins after a community referendum.
• 1992: monitoring for cyanobacteria (blue-green algae) in source and drinking water begins.
• December 15, 2011: City Council votes to continue fluoridation.
• 2015: testing for cyanotoxins, the toxins some algae produce, is added in Lake Austin, Lake Travis and finished water from all three plants. Raw lake water is checked for algae at least weekly.
• 2020: a copper sulfate feed system is installed to keep zebra mussels out of raw-water piping. The mussels can damage equipment and affect taste and odor.
• 2021: after Winter Storm Uri, plants are repaired and winterized for future hard freezes.
• October 2024: after a multi-year inventory of every public service line, Austin Water confirms its public system has no lead pipes.
• October 2025: responders practice handling a simulated oil spill drifting toward the Ullrich plant's intakes near Tom Miller Dam, with the LCRA, TCEQ and Austin Watershed Protection.

2025 numbers worth knowing

Hardness ranged from 70 to 126 ppm and averaged 93 ppm (5.4 gpg). That's moderate: enough to spot glassware, not enough to make a softener an obvious purchase. Our salt cost calculator shows what one would cost to run. Disinfection byproducts were well under their limits. The highest locational running annual average was 15.6 ppb for HAA5 (limit 60) and 45.5 ppb for total trihalomethanes (limit 80). Lead is tested at customer taps every three years. In the 2024 round the 90th-percentile result was under 1.0 ppb, and no sample exceeded 15 ppb.

PFAS: “little to no,” with detail

Austin Water's report describes “little to no detectable traces” of PFAS. EPA's UCMR 5 data for the system gives more detail. Across 12 samples, six compounds were found at least once. The highest was PFBA at 8.4 ppt, then PFHxS at 6.2 ppt (found in 6 of 12 samples) and PFOS at 4.8 ppt (2 of 12). Those are single-sample maximums, not the annual averages the new federal rules use, but they explain why the utility hedges with “little.” If PFOS or PFHxS matters to you, a certified reverse osmosis or carbon filter is the household fix. Our filter selector lists the certifications.

Algae season

Warm, nutrient-rich lake water lets cyanobacteria multiply into surface blooms, and some produce toxins. That's why the utility samples both lakes and treated water, and samples more often as conditions change. Advisories for swimming or pets in the lakes are a separate question from tap water. The report's testing covers what leaves the plants.