Consumers know less about the water they pay dearly for in bottles than what they can drink almost for free from the tap because the two are regulated differently, researchers and congressional investigators say in new reports.

Both the Government Accountability Office and the Environmental Working Group, a research and advocacy organization, recommend in reports being released Wednesday that bottled water be labeled with the same level of information municipal water providers must disclose.

The researchers plan to urge Americans to make bottled water "a distant second choice" to filtered tap water during their testimony before a congressional subcommittee Wednesday morning.

Bottled water — an industry worth about $16 billion in sales last year — has been suffering lately as colleges, communities and some governments take measures to limit or ban its consumption. As employers, they are motivated by cost savings and environmental concern because the bottles create unnecessary waste and can be hard to recycle.

Bottled water sales were growing by double-digit percentages for years and were helping buoy the U.S. beverage industry overall. But they were flat last year, according to trade publication Beverage Digest.

Beverage Digest editor John Sicher said some consumers are turning on the tap during the recession simply because it's cheaper.

From 1997 to 2007, the amount of bottled water consumed per person in the U.S. more than doubled, from 13.4 gallons to 29.3 gallons, the GAO report said.

The issue on Wednesday though, before a subcommittee of the Energy and Commerce Committee, was less about waste and water quality concerns and more about the mechanics of regulating bottled water.

As a food product, bottled water is regulated by the Food and Drug Administration and required to show nutrition information and ingredients on its labels. Municipal water is under the control of the Environmental Protection Agency.

The two agencies have similar standards for water quality, but the FDA has less authority to enforce them, the GAO said, and the environmental agency requires much more testing.

The GAO noted the FDA also has yet to set standards for chemicals called phthalates, found in many household products, while the EPA limits their presence in tap water.

In a survey of officials in all 50 states and the District of Columbia, the GAO found they think consumers are misinformed about bottled water.

"Many replied that consumers often believe that bottled water is safer or healthier than tap water," according to the GAO report.