Preventing the intrusion of rain into the exhaust of your system will stop the negative effects of water on your system. Water can contribute to the corrosion of components, especially fan and electrical elements. A well-designed rain cap is one solution to this problem. As the name implies, the unit serves as a cap over the exhaust pipe. The cap is larger than the diameter of the pipe and affixed to the pipe and includes side vent panels or openings that allow for the flow of the air to the outside with minimal restrictions to exhaust airflow. Rain caps can cause some backflow pressure and are a good solution for those systems that can accommodate these restrictions.