Drinking Tap Water
Depending on the region, the quality of tap water vary with more or less minerals. However, in general it is safe to drink the tap water in Germany.
label at a public restroom at Frankfurt Airport
Some people in Germany don't drink the tap and buy mineral water instead. Some friends of ours have been drinking tap water years. So if you want to safe money while travelling, just fill up your water bottle at a clean water tap.
Even though the tap water is safe drink in Germany, restaurant won't serve a complimentary glass of water. So you need to order a pricy glass of mineral water (or other drink). It is very uncommon to ask the waiter for a glass of tap water. A friend visiting from England actually tried though and succeeded after some confused looks from the waiter.