Austin’s current boil water notice is the third time ever residents have had to boil their water before drinking or cooking with it — and all three of these alerts have been issued in the last four years.

Here’s why a boil water notice happens, and what you should know about current guidelines:

How Austin’s water treatment process works

The city’s water system — which serves more than one million residents — processes and treats 335 million gallons of water per day.

To do this, Austin Water sources water from the Colorado River and processes it at three treatment plants around the city, undergoing several steps of filtration, cleaning, and treatment. The whole process takes 6-10 hours.

Previous boil water notices

2018: In October, Central Texas experienced historic flooding, which sent large amounts of mud, silt, and debris into the water system. This slowed filtration + put treatment plants at ⅓ capacity. The resulting boil water notice was the first time in the history of the city, and lasted seven days.

2021: Winter Storm Uri resulted in mass blackouts and several days of below-freezing temperatures. The city’s main Ullrich treatment plant lost power, water pressure dropped below minimum standards, and infrastructure suffered freeze damage and leaks. This boil water notice lasted for six days, until crews were able to repair the leaks and bring plants back online.

2022: Although some were concerned about impacts from last week’s freeze, the current boil water notice issued Saturday was caused by a staff error, not weather. The system is currently experiencing issues with turbidity, or murkiness, due to a mistake made during the treatment process.

Austin Water is currently waiting for water quality test results — some of which take 24 hours — that show the water is safe for drinking. In the meantime, the city has given out 7,000+ cases and 6,000+ gallons of water at local distribution sites. Officials expect the notice to end tonight.