New stupid question - My understanding (such as it is) is that in colder areas of the US people have basements so that the area around their water pipes is warm and they don't freeze in winter. Is that right? If so, my stupid question is - what about the mains water before it reaches the house? What stops that from freezing?
Actually, its for more than just pipes.
The foundation of any structure needs to extend below the frost line. The ground shifts a little when the water in it freezes and thaws. The house is more stable if the foundation goes below that.
Where I live the frost line is at about 3.5 feet. My foundation has to extend at least to 4 feet. If you have to dig that deep anyway you might as well go to 6 feet and get some extra usable space in the house. That space is perfect for the furnace and the water heater. My area gets tornadoes, so most people have a room in the basement where they can hide when a tornado is in the area. Thats another reason to have a basement.
And yes, my water line enters the house through the basement. It keeps the water in the line from freezing.