Usually in Latin American countries it’s not very safe to drink tap water, however Costa Rica (and Chile) is an exception. It's generally safe to drink tap water in Costa Rica, except in the most rural and undeveloped parts of the country. Typically, the further inland you go, the better the chances of clean water you will find. However, if you prefer to be cautious, buying bottled water is your best bet. If you have the means, vigorous boiling for one minute is the most effective means of water purification.