MARY LOUISE KELLY, HOST:
The city of Houston is under a boil water notice due to a power failure at one of the city's main water purification plants. Houston Public Media's Andrew Schneider reports city leaders are still trying to understand why, but they hope to restore clean water by Tuesday.
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ANDREW SCHNEIDER, BYLINE: At a Houston Costco, residents filled their shopping carts with cases of bottled water. Among them was Aanchal Raisahib, who learned of the outage this morning on Instagram.
AANCHAL RAISAHIB: So I spent about an hour boiling water just to brush my teeth and do all that stuff. And then I realized I don't have drinking water and I might need backup. And I don't know how long this is going to last. So I'm here buying water.
SCHNEIDER: Some 2 million people are affected. Houston is the country's fourth-largest city. Many school districts in the area closed today. Some non-emergency medical procedures were postponed. The water problems started Sunday morning. Three plants within one of the city's main water purification facilities all lost power. Houston Mayor Sylvester Turner explained what happened.
SYLVESTER TURNER: The first transformer fell, and then the redundant one was the second transformer, which coincidentally and uniquely also fell.
SCHNEIDER: That caused pressure to drop sharply and raised the risk of bacterial contamination of the water supply. The city didn't issue the boil water notice until many hours after. Turner said the delay was due to conversations with the Texas Commission on Environmental Quality, or TCEQ, on whether such a step was warranted because the drop in pressure was so brief. Turner said there likely wasn't contamination, but TCEQ is testing water samples to be sure.
TURNER: Our hope is by late tonight or early tomorrow morning, we'll get a positive response from TCEQ and that the boil water notice can be lifted.
SCHNEIDER: It's not clear why both the facility's transformer and its backup failed. The mayor has asked for an explanation. This is the third time in as many years that the city has been without clean water for an extended period. In 2020, a major pipe burst. And last year, Winter Storm Uri knocked out water and power for days.
For NPR News, I'm Andrew Schneider in Houston.
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