There are several ways to find your septic system lid, including: Visual Inspection - look around your yard, look for very green patches of grass or wet patches. Poke The Ground - poking the ground every few feet with a metal probe/locator tool can help find the septic lid (which can be from 4 inches to a foot deep). Follow Piping - Go to your basement or crawl space, and then look for the main sewer line that leads to your septic tank. Look for a pipe that's roughly four inches in diameter, then go outside to look on the other side of the wall and follow the direction it’s pointing in.