With one short answer: YES! Not only safe to drink, but really high quality as well. We have this luck In Ljubljana that groundwater doesn't have to be treated with any technical water preparation procedures, and is only chlorinated on rare occasions. From 5 main water supply facilities and few local ones it than runs through some of 1.100 km of water network to the end user. It doesn't stay in the system for more than few hours, so your glass of water will always be fresh :)