NEW YORK (CNN) -- Pepsi-Cola announced Friday that the labels of its Aquafina brand bottled water will be changed to make it clear the product is tap water.

The new bottles will say, "The Aquafina in this bottle is purified water that originates from a public water source," or something similar, Pepsi-Cola North America spokeswoman Nicole Bradley told CNN.

Pepsi will change current labels on water bottles to say the water comes from a public water source.

The bottles are currently labeled: "Bottled at the source P.W.S." Americans spent about $2.17 billion on Aquafina last year, according to Beverage Digest, an independent company that tracks the global beverage industry. The U.S. bottled water business in 2006 totaled roughly $15 billion, it said.

No timetable was available for when customers will see the label change on store shelves, another Pepsi spokeswoman, Michelle Naughton, told CNN.

Pepsi released a statement saying: "If this helps clarify the fact that the water originates from public sources, then it's a reasonable thing to do."

Coca-Cola does not have plans to change the labeling on its Dasani brand bottled water, a company spokesman told CNN, despite the fact the water also comes from a public water supply.

Dasani's U.S. sales totaled approximately $1.89 billion in 2006, according to Beverage Digest calculations.

Nestle also has announced it will be changing the bottles of its All Nestle Pure Life Purified Drinking Water to "identify the source of the water, whether it's from a municipal supply or ground-water well source."

That change "will be showing up on labels this year and is expected to be on all of these labels by the end of the first quarter of 2008," the company said in a written statement.

Nestle has not decided what the new labels will say exactly, a spokesman told CNN.

All Nestle Pure Life Purified Drinking Water sales in the U.S. totaled $1.17 billion in 2006, Beverage Digest reports, a large portion of Nestle Water North America's total U.S. sales of $3.57 billion for the year, reported by Nestle.

Corporate Accountability International - which describes its work as challenging "irresponsible and dangerous corporate actions around the world" - has been pushing for this change for months with its nationwide "Think Outside the Bottle" campaign, said spokeswoman Deborah Lapidus.

Its aim was "to challenge the marketing muscle of the bottled water corporations and to galvanize support for our public water systems around the country," she said. The campaign focused on Nestle, Coca-Cola and Pepsi.

According to a 1999 report by National Resource Defense Council, an environmental advocacy group based in Washington, "about one-fourth of bottled water is bottled tap water [and by some accounts, as much as 40 percent is derived from tap water] - sometimes with additional treatment, sometimes not."

Shares of Pepsi (down $1.18 to $65.66, Charts, Fortune 500) closed down 1.7 percent to $65.66 on the New York Stock Exchange, while shares of rival Coke (down $0.70 to $52.28, Charts, Fortune 500) closed down 1.3 percent to $52.28.