Whether you’re planning a backcountry trip or an urban adventure abroad—say, an Annapurna Circuit trek in Nepal, or a cultural tour of its capital, Kathmandu—you’ll want to take extra precautions with your drinking water. In many developing countries, both municipal drinking water and backcountry water are prone to viruses in addition to bacteria and protozoa. Bringing a water purification system with you is a smart way to help protect you from viral infections that can jeopardize your health, not to mention ruin your vacation. There are a few water treatment options available to you that target different qualities of water. A general rule when treating water is to start with the clearest water possible, but sometimes your options are limited. Here’s what you should know about treating water when traveling…