This, of course, is a no-brainer, but sometimes inadvertent location of supply or even drain lines can result in frozen pipes during cold weather. Keep all supply lines within the conditioned space and within interior wall or ceiling cavities. In very cold climates, even pipes located on the warm side of fiberglass insulation in an exterior wall can be subject to freezing.

Do the same if you must run supply lines in the band joist area or floor cavity of an uninsulated crawl space or basement. It is best to insulate crawl spaces and not vent them to the outdoors.