Broken pumps, burst pipes and chemical shortages have left millions without potable water after this week's devastating winter storm.

The big picture: Millions of people across the South have been told to boil water, with thawing temperatures expected to reveal the extent of the damage to infrastructure.

• Texas: 7 million people  — because low water pressure could have allowed bacteria to seep into the system, AP reports.
• Tennessee: 260,000 homes and businesses in the Memphis area — because of water main ruptures and problems at pumping stations.
• Mississippi: Most of Jackson's 161,000 residents — because the city ran out of chemicals due to resupply issues.

Between the lines: Water mains will need repair and homes have frozen pipes that will fail as they warm up. Municipal systems will take time to recover.

What's next: Houston Mayor Sylvester Turner (D) said he expects residents will have drinkable tap water again next week.