This post has been updated.

The bottled water industry and the National Park Service have been wrestling for eight months over the parks’ campaign to slash sales of disposable water bottles to visitors to reduce the litter they leave behind.

This week, Big Water’s allies in Congress put the parks on the defensive with language in the budget deal reached by congressional negotiators. It requires the agency to justify each park’s bottled water ban and calculate how much it saves in recycling and landfill costs to dispose of park waste.

The order falls short of what the International Bottled Water Association has pursued behind the scenes for many months, a law that would  prohibit the Park Service from using taxpayer money to replace plastic water bottles with refilling stations.

But the congressman who tried to make good on that strategy by adding a last-minute amendment to an Interior Department appropriations bill last summer said he’s laid the groundwork to come back next year for another fight.

“We’ve preserved the issue,” Rep. Keith Rothfus (R-Pa.) said in an interview Wednesday. “If the Park Service cannot provide the justification for a policy that seems to have no real benefit and is an inconvenience for families, we’ll be back.”

Park Service officials, who were unaware of the language in the budget bill until a reporter notified them, declined comment and referred calls to the White House.

The edict is a first-step resolution in a drama featuring fiery warnings on the House floor of families dehydrating in the Grand Canyon in 100-degree heat, a sit-in by environmental groups, letter-writing campaigns on both sides and lobbying by a $13 billion industry.

Environmental groups characterized the new mandate for the Park Service as a win for their side, given that it does not go as far as the industry’s goal of stripping federal funding from efforts to build refilling stations.

“The defeat of the industry-supported [Rothfus] amendment is a clear victory for our national parks and the millions of people who love them,” John Stewart, deputy campaign director for the watchdog group Corporate Accountability International, said in a statement. “It’s more important than ever that our elected officials prioritize people and the environment over the corporate profits of the bottled water industry.”

Stewart’s group and a coalition of environmental groups have led a grass-roots campaign against the effort to stop the parks from swearing off bottled water, including a sit-in in Rothfus’s office in November.

On Wednesday, 33 House Democrats signed a letter  to Park Service Director Jonathan Jarvis urging him to hold strong to a policy they called a “beacon of sustainability that educates millions of park-goers about the importance of reducing their carbon footprint and preserving our public water supplies.”

The confrontation started gradually. Facing overflowing garbage cans and ever-growing recycling and landfill costs, Jarvis told 408 parks, national monuments and historical sites across the country in 2011 that they could eliminate sales of disposable plastic water bottles, as long as refilling stations and reusable bottles replaced them.

Bottled water itself is not banned from the parks. Visitors can bring as many of their own bottles in as they want.

As of this week, 22 parks have banned sales, the Park Service said, including the Grand Canyon, Canyonlands, Arches, Zion and Bryce Canyon, with Fort Sumter National Monument announcing plans on Wednesday. Refilling stations cost anywhere from $2,000 to $15,000, Norton said, depending on how much pipe must be laid to a water source, which often is a spring.

It’s a fraction of the park system, and a fraction of global bottled water sales are at risk. But the industry rallied hard against the policy this year, starting a public relations campaign that accuses the parks of reneging on their pledge to encourage a healthy lifestyle.

In a statement Thursday, the bottled water association commended Congress for “requiring the National Park Service to provide the facts about how it justifies banning the sale of bottled water…”

“IBWA is confident a report detailing the data individual national parks used to ban the sale of bottled water will lead to the conclusion that such bans provide no benefit to park visitors,” it said.

The Park Service has 60 days to report to Congress. The budget language may seem benign for the agency, but it’s strategic. By asking the parks to justify their bans on bottled water sales in economic terms, Congress hit a weak spot. The Park Service has said it is nearly impossible to separate water bottle costs from the waste stream, and calculating a direct savings to recycling costs won’t be easy.

Rothfus, whose state has a $5.5 billion bottled water industry, according to the water association, said he shared his concerns with budget appropriators on Capitol Hill about a month ago.

“The family is going to give their kid Gatorade or Coke and not water, so what’s the utility of that?” he said Wednesday. “You’ve taken away a healthy alternative for a family. If your kid is going to have a sugary drink, that’s not a benefit.”

Rothfus said his 8-year-old daughter has a health condition that puts her at risk for dehydration, heightening his awareness of the risks of not having ample bottled water available in a park.

Even if parks sell reusable bottles, “You have to wash them,” he said. “They’re not necessarily dishwasher-safe.”

In June the congressman denounced the policy on the House floor, decrying the health dangers of depriving park visitors of a healthy alternative to Coke.