When the local water isn’t potable, travellers and locals often think that their only choice is to buy safe, sealed H2O. Even in the United States and other tap-safe countries, bottled water consumption is rampant.

But the growing waste from plastic water bottles is a problem around the world.

Empty bottles, made of petroleum-based plastic, accumulate as non-biodegradable rubbish along city streets, in rivers, in parks, on beaches, and ultimately, they can end up in the ocean. Floating in the Pacific is the Eastern Garbage Patch, a large heap of trash twice the size of Texas, according to the Los Angeles Times. The vast majority of it is plastic.

So, what’s the solution for litter-strewn locations? Several tourism officials and travellers themselves are making a difference. 

Banning the bottles
One way to stop plastic-bottle-clutching tourists from littering is to ban bottled water outright. Italy’s Cinque Terre national park – a breathtaking string of cliff-perched villages along the Mediterranean coast – banned the bottles in 2010. This year, the US National Park Service banned the sale of plastic water bottles at Grand Canyon National Park, where they made up 20% of the park’s waste.

Both parks asked tourists to fill reusable containers at public fountains or water filling stations -- Italy’s even offers a choice of sparkling or still. Franco Bonanini, president of the Cinque Terre national park, told London’s Telegraph newspaper that its three million annual tourists were leaving behind too much rubbish. "With so many visitors, the footpaths and villages of the Cinque Terre are at risk of being transformed into a great big open-air dustbin,” he said.

Building houses
Several projects around the world are using plastic bottles as building materials. Instead of piling up in a stream or a landfill, the bottles are packed full of sand or trash and used as a brick. The eclectic building block was used to construct houses, and even a water tank, in Honduras by a German man named Andreas Froese, who went on to launch an organization called Eco-Tec, with bottle-building projects in several countries.

The unusual architecture of these structures made them into tourist sites themselves, as northern Nigeria discovered last year. Other initiatives, such as this Argentinean project, make more traditional-looking bricks by grinding the plastic bottles and mixing them with cement.

One bottle at a time
Individual tourists can do their bit by carrying their own reusable bottles and filling up with fresh, clean water whenever they can. Eco-conscious hotels in areas without potable water are offering water-filling stations, and those that don’t might be willing to boil water on request. Tourists can also treat their own water with purification devices, and there’s no need to suffer the poor taste of iodine tablets: lightweight systems, such as ultraviolet light purifiers, don’t leave an aftertaste.

Travellers without reusable bottles or purifiers can buy big containers to keep in their hotel rooms, rather than tossing five or six small bottles in the trash every day. After all, those bottle-brick houses may look cool, but there’s no shortage of plastic construction material.     

Lori Robertson writes the Ethical Traveller column for BBC Travel. You can send ethical dilemmas to bbcethicaltravel@gmail.com.