Is it safe to use heat tape on inside water lines?

Yes, that would have helped with doors opened and get up a few more times during the night and run the water. The main place I had issues was just inside the camper where the water come from the outside and no door to open to get heat in there. I unscrewed the acess hloe in the floor of my bedroom closet to find this area. Has also thinking placing a lightbulb in a shield in that area.