Nepalese tap water is not safe to drink. Bring water purifying tablets or a water purifying stick to save money and the environment. Note that at higher elevations during the coldest times of year the water will freeze, so you’ll need to buy boiled water from teahouses. Buy a decent thermos flask or plastic water container in Kathmandu so that you can top up with hot, boiled water at the beginning of the day – starting with hot water will stop it freezing.