In the north, most of the pipes run through the basement and inside of the (preferably interior) walls if the house has more than one story.
Most northern houses have basements. Once you've dug down four feet to get the foundation below the frost line, you may as well keep digging another couple of feet to obtain useful storage and utility space. (Nowadays, they usually go to eight, but my vintage 1948 basement is about 6 feet.)
Cindy Hamilton