Call it a tempest in a tub.

The famed "natural mineral water" baths at Saratoga Spa State Park have been diluted with regular tap water for two decades, state officials confirmed Monday. The New York Post, which first reported the story, claimed that tens of thousands of customers who pay $20 for the privilege of soaking in the bubbly water have been deceived.

"I thought I was bathing in pure mineral water," 22-year-old Kristina Weilbacher, of San Antonio, Texas told the newspaper. "I didn't know that. I definitely should have been told."

The state and the company that operates the baths, Xanterra Parks & Resorts, mix heated public drinking water with the chilly carbonated mineral waters pumped up from more than 1,000 feet below ground. The Post said the mixing began after the mineral water heater used by the park since the 1930s broke down. The baths attract about 14,000 customers a year.

"They're lying to the public. It's the state committing fraud," Raymond Watkin, a former Saratoga Springs mayor, told the Post.

State parks spokeswoman Eileen Larrabee said the state has never had a consumer complaint about the water mix, a practice she said is not unique to the Lincoln and Roosevelt baths at Saratoga. But she said the state wants to make sure consumers are fully informed about the makeup of the baths.

"We need to clarify that practice," Larrabee said.

Calls to the baths and Xanterra's Colorado headquarters were not immediately returned.

State Senate Majority Leader Joseph Bruno, who represents the city, called on the Spitzer administration to investigate. In a prepared release, the Republican leader said: "The report that ordinary tap water has been secretly used at the baths could damage Saratoga's reputation and be harmful to business and tourism."