How is tap water treated? What causes a boil-water advisory?

We take our tap water for granted until we’re told we can’t drink it. (Photo: Latte Art/Shutterstock)

In the wake of hurricanes and resulting power outages, many times people are told their tap water is non-drinkable. Water providers often issue a “boil-water advisory” because a treatment facility was affected during a storm. Residents are typically told that water is safe for bathing and laundering clothes.

But even though the water that comes out of the faucet looks the same as it always does, something obviously happened to make it no longer potable, or safe to drink.

So what exactly occurred? And what does the water treatment facility do to the water in the tap in first place?

Most municipal water treatment plants work by taking surface water, like water that comes from streams or lakes, and putting it through the treatment ringer, with processes like coagulation, filtration, sedimentation and disinfection. All of these processes help to eliminate contaminants in the water, like shigella, E. coli and cryptosporidium.

If a water treatment facility is flooded, as it could be during a hurricane , it is possible that the entire treatment facility’s integrity could be compromised, since the system can […]

Full article: How is tap water treated, and what causes a boil-water advisory?

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