In Japan, the answer to whether "toilet water" is drinkable requires a bit of clarification regarding plumbing. The tap water in Japan is among the safest and highest quality in the world, regulated by strict standards from the Ministry of Health, Labour and Welfare that often exceed WHO guidelines. This means the water coming out of the bathroom sink in your hotel or a public restroom is perfectly safe to drink. However, you should not drink the water directly from the toilet bowl or the "flush" tank for obvious sanitary reasons. Interestingly, many Japanese toilets feature a small sink on top of the tank where clean water flows out when you flush so you can wash your hands; this water then drains into the tank to be used for the next flush. This specific "hand-washing" water is tap-pure and technically drinkable, though most people find the idea unappealing. In some older buildings or very remote rural areas, non-potable "recycled" water (greywater) might be used specifically for flushing toilets to conserve resources, but these are almost always marked with a sign. In 99% of modern urban settings, the water supplied to the entire bathroom—sink, shower, and toilet—comes from the same treated municipal source, making the sink tap the ideal place to refill your water bottle.