Whether you can drink tap water depends entirely on the destination's water treatment infrastructure and your own gut sensitivity. In most of Western Europe, Canada, Australia, Japan, and the United States, tap water is treated to high safety standards and is perfectly safe for consumption. However, in many parts of Central and South America, Africa, and Southeast Asia, the water may contain bacteria, viruses, or parasites like Giardia to which locals are immune but travelers are not. Even in countries with "safe" water, old lead pipes or heavy mineralization can cause stomach upset. A good rule of thumb is to look at the CDC’s Travel Health notices for your specific country. If the water is deemed unsafe, avoid not just drinking it, but also using ice cubes, brushing your teeth with it, or eating raw salads washed in it. For eco-conscious travelers, using a water bottle with a built-in "hollow fiber filter" or a UV-purification light (like a SteriPen) is a safer and more sustainable alternative to relying on single-use plastic bottled water.