National parks in Utah are reporting less trash in their bins thanks to bans on selling bottled drinks within the parks.

Arches and Canyonlands National Parks have seen 15% less overall waste, including 25% less material in the recycling bins. Zion National Park estimates its ban prevents more than 5,000 pounds of plastic bottles ending up in the trash every year.

But Arches Facilities Manager Tommy Johnson says many visitors still bring their own cases of bottled water.

“Even though we quit selling the bottled water here in the park, they’re everywhere,” he says.

Johnson says when Arches implemented the ban, it began selling reusable water bottles and installed a water treatment system and filling station at the visitor center.

“When we quit selling them we put that in so that the visitors wouldn’t be so set back because they couldn’t buy bottled water,” he says. “Now they can get it right out of the tap at the visitor’s center and it’s just like drinking bottled water.”

Four of Utah’s five national parks have bans on plastic bottle sales. But the trend has been slow to catch on nationally; only 22 national parks in the country—about 5%—have a ban.