plumber here, exterior pipes can clog up easily when its cold because any trickle of water will freeze in the pipe same as how icecicles are made and itll keep growing till it plugs up the line with ice. you can get heat tape to try and deal with it but thats not guaranteed to work. the other problem is when the pipes are freezing cold and your using hot water the lines have a tendency to split right down the middle from the temperature change. if that happens you gotta replace it all.

a couple of years ago when i was doing service plumbing in baltimore i saw a house that had a huge water bill because the neighbors had connected a garden hose between the two homes hose bibbs to steal water because theirs had been turned off.