AUSTIN (KXAN) — Austin’s water system leaked 854 million fewer gallons of treated water in 2021 than the year before, marking the city’s largest reduction in year-over-year water losses in almost a decade, according to a system audit.

In 2020, Austin’s pipes leaked a record 7.34 billion gallons. That dropped to 6.49 billion gallons last year, according to a yearly report submitted to the Texas Water Development Board.

While 6.49 billion gallons is a huge amount – nearly enough to fill Inks Lake one-and-a-half times – Austin Water officials said it is within acceptable industry limits. In financial terms, last year’s leaked water cost the city over $2.5 million, according to the audit.

Water officials use the so-called “infrastructure leakage index,” or I.L.I., as a measure of overall system performance. The leakage index is based on a formula that includes the operating pressure, number of connections and length of city pipes. Some water loss in a system the size of Austin’s is unavoidable.

In 2021, Austin’s leakage index “dropped from 4.45 to 3.86, which is within the range suggested by the American Water Works Association (AWWA) and the Texas Water Development Board (TWDB) of between three and five for utilities of our size, customer base, and production levels,” said Ginny Guerrero, an Austin Water Utility spokesperson.

Austin Water has several initiatives helping address water loss, including fast response to reported leaks, infrastructure renewal investment, proactive leak detection and prevention, and using best practices and innovation, Guerrero said.

Austin’s water system has over 3,900 miles of pipes ranging from two to 84 inches wide. The city has a program to replace and rehabilitate aging pipes. Austin is also swapping out 240,000 old water meters with new smart meters by 2025, according to a city briefing.

The city’s 6.49 billion in leaks is a measure of “real” water losses, which is physical water lost from pipes. There are also “apparent losses” – a term for accounting losses, like unbilled water use. Austin had 1.5 billion gallons of apparent water loss last year that cost the city $8.1 million, according to the audit report.

The drop in leaked water is some good news for a utility that’s endured a few turbulent years.

In February, staff errors at the Ullrich water treatment plant allowed tainted water to enter the city’s system, prompting a city-wide boil water notice. Former utility director Greg Meszaros acknowledged oversights and resigned his post on Feb. 11. It was the city’s third boil-water notice in four years.

During an epic winter storm and freeze in February 2021, thousands of homes experienced broken pipes and electricity outages. Austin’s largest water plant lost power, leading to a boil water notice.

In 2018, flooding caused excessive muddiness in the system’s water sources, which triggered the utility’s first ever city-wide boil water notice.

In 2019, zebra mussels in a water plant intake pipe caused thousands of customers to get foul smelling water at the tap. The city did not issue a boil-water notice, assuring that despite the odor the water was safe to drink.