How can I install a downspout extension underground to improve the drainage system around my home?

To install a downspout extension underground, you will need to dig a trench from the downspout to the desired location for the extension. Place a PVC pipe in the trench, ensuring it slopes away from your home. Connect the pipe to the downspout using a connector. Cover the pipe with gravel and soil, and test the system by running water through the downspout.