We just purchased a home and the seller hired a handyperson to run a pipe for the hot water heater pressure release. They ran a copper pipe down...at the bottom there's an elbow that's connected to another pipe that exits through a hole they drilled to the outside. The outside of our house has stucco. What do I do to seal the gap around the copper pipe? Do I just use some caulk? I basically want to prevent rain water from leaking into the gap.