At low-level concentrations, the cancer-causing chemical can turn clear water yellow, and when it’s really bad, a water source contaminated with ‘chrome-6’ can flow purple.
But even when tap water is perfectly clear, Brockovich admitted she’s still "funny about water," and rarely, if ever, drinks straight from a tap.
"I think we’re pretty convinced that these chemicals are immune toxicants that we should be concerned about," Linda Birnbaum, a microbiologist who directs the National Institute of Environmental Health Sciences at the National Institutes of Health, said last month.
Eight big chemical companies in the US (including DuPont and 3M) voluntarily phased out the chemicals in their products and replaced them with new ones by 2015.
How to ensure your water is safe to drink The first thing you can do if you’re worried about the quality of your tap water is read your local water report.
She has even agreed to endorse a filtering product for the first time ever: the AquaTru home water filter.
Plus, bottled water is often just treated tap water, and the products are generally less regulated than what comes out of the tap.
But the Food and Drug Administration (FDA) lets companies use the label "purified water" on water that’s been treated in several different ways, so it’s not always clear how it’s been filtered.
"I let consumers know, use your own common sense … if it looks funny or smells funny, don’t drink it."
Water-quality data for cities and towns around the country is required to be reported every year, and it’s available on the EPA’s website.