Depressurization, another major cause of contamination, occurs when firefighting efforts remove large amounts of water from the system in a short period of time. “The water line that connects a house usually puts out about 9 gallons per minute,” says Whelton. So if you run five or six pump trucks from the water line, you’re looking at thousands of gallons of water being removed from the water system in a short amount of time.

When that happens, the water pressure drops, and the system becomes vulnerable to bacteria or chemicals entering the system from the surrounding environment. Typically, the high water pressure within the system prevents any external contaminants—such as soil or groundwater—from finding their way into the system’s components.

Structural damage from fires can also result in loss of pressure, Whelton said. In the case of large fires like the Palisades or Eaton fires, you can have large volumes of water dumping, out of control, out of the system, due to pipes and other parts of the system bursting. If there is damage, smoke and debris can be sucked into the water system, while damaged sewage lines can leak into drinking water pipes that run nearby. “When the water utility system starts trying to repressurize, they start pushing the contaminated water through the infrastructure again,” said Whelton.

During the Marshall Fire in Louisville, Colorado in 2021, which burned more than 1,000 homes, city officials advised residents to use mains water only for flushing until extensive testing confirmed safety. . Given that more than 12,000 structures had burned in Los Angeles as of Monday morning, the potential for widespread contamination is significant, Kearns warned.

The coming days and weeks will be crucial. Once water experts assess the damage, they can determine if the system can be cleaned clean or if infrastructure repairs are needed. When enough has burned, the workers have to replace the pumps, pipes, and even tanks. For parts of Los Angeles County served by LADWP, McCurry estimates this recovery could take anywhere from a few days to weeks.

Altadena and the surrounding regions, however, are served by several smaller water providers, such as Lincoln Avenue Water Company, Las Flores Water Company, Rubio Canon Land and Water Associationand Kinneloa Irrigation District—all of which issued Do Not Drink notices. “In the case of a large water system like LADWP, you’re probably going to see things move faster,” Kearns said. “For small water providers, who sometimes have only a few employees and don’t have budgets for these types of events, they can have some struggles.” Santa Cruz experienced similar challenges during the CZU Lightning Complex Fire in 2020, where water service took months to stabilize. McCurry warned that some regions could take years to build from scratch or repair large systems that have burned out.

It’s important for residents to stay informed about recovery efforts, because alert systems can be complicated, and many residents don’t even receive them, Kearns said. People should “actively look for any boils or Do Not Drink water alerts from your water supplier, your city, your county,” he advised. “Share that with your neighbors and make sure any people who have languages ​​other than English as a first language get the alerts and understand what’s going on.”

Other places, such as Louisville in Colorado, and Maui in Hawaii, have released public access maps that track water quality in each plot of land, helping to inform residents in the months and years that follow. .

Before the advisory is lifted, water providers are legally required by the State of California to monitor for benzene. However, Whelton cautioned that benzene is not the only chemical of concern and the list of potential contaminants is long. Government and third-party testing services do not always account for every possible exposure. “It’s possible that some of those chemicals may be around longer than the water providers expect,” McCurry said. He still recommends remaining cautious. Activated charcoal filters can help remove some organic contaminants, but they may not completely eliminate the hazards.

“Safe water CAN can be restored after the fire,” said Whelton. “Communities that recover quickly and are stronger are those that work together and support each other.”