taste. >> abc news water challenge. step right up. >> they didn't know what they were drinking but they knew what they thought. >> tell me if you prefer the taste of a or b. >> b. >> b. >> what do you like about a? >> it feels cleaner. >> reporter: why do you like b more? >> fresher. >> b. >> reporter: the results were mixed. but now the more serious question, do you think that bottled water is healthier for you? environmental advocate mae wu says think again. >> we've done studies that have shown that bottled water is no more safe or clean than regular tap water. >> there is more testing of bottled water than tap water. >> actually there is more testing of tap water than bottled water. >> reporter: that's right. by federal rule, they test tap water for 100 compounds every day with results online for you to read. bottled water doesn't have to do that. but some say they exceed the federal requirements. >> bottled water is a safe, healthy, convenient product. consumers like the fresh taste. >> reporter: which brings us back to our taste test.