What began as a public relations campaign to encourage people to switch from bottled water to tap water has turned into a brisk business.

A year ago Eric Yaverbaum, president of the public relations company Ericho Communications, and Mark DiMassimo, founding partner of the DiMassimo Goldstein advertising agency, created Tappening, a campaign and a Web site (www.tappening.com). They intended to educate the public about the petroleum consumed to make disposable water bottles and the huge burden the products impose on landfills.

The strategy, DiMassimo says, was to “unsell bottled water.” To help offset the cost, the partners decided to market reusable water bottles on their site, each one bearing one of two slogans: “Think Global, Drink Local” or “What’s Tappening?” They received 39,000 orders within 36 hours. “I learned very quickly the potential power of viral marketing,” Yaverbaum says. The surprise prompted the duo to ramp up their publicity machinery, which garnered national attention. Although that response cannot be linked directly to the fate of the industry, both PepsiCo and Coca-Cola reported a decline in sales for unflavored water in the second quarter of 2008.

By this past November, Yaverbaum and DiMassimo had sold more than 300,000 bottles. The Web site now offers numerous articles, home water-testing kits and a national tap-water-quality database. “What bottled water has is a brand,” DiMassimo explains. “That’s what we aim to create for tap water.”