Most of Tenerife drinking tap water comes from desalinated sea water and doesn't have a good taste, it's fine for bathing or washing clothes, etc. For drinking, tea, coffee or ice always use bottled water. Some people experience upset tummies and other digestive problems that possibly are caused by the tap water.
Is it rude to tip in Tenerife?
There's no need to worry too much about tipping etiquette in Tenerife or the rest of the Canary Islands. In most cases, it's enough to just round up the sum to an even amount (depending on the initial sum of course).