To locate a septic tank's lid, stick a thin metal probe into the ground to outline the dimensions of the tank, and then dig a shallow excavation which will reveal the lid. If the tank was installed before 1975, it will have one concrete lid in the center. If the tank was installed after 1975, it will have two fiberglass or polyethylene lids centered at either end of the tank.
Only trained professionals should open a septic tank lid. Dangerous fumes are often emitted from the tank, and falling into a tank can be fatal due to toxins. Another difficulty experienced by homeowners, usually after purchasing a property with a septic tank, is locating the septic tank itself. An easy way to do this is to locate the 4-inch drain pipe located in the basement or crawlspace. This pipe transports waste water from the house to the tank. Mark the location of the sewer pipe on the outside of the house, and then stick a small metal probe into the ground to locate the sewer pipe. Follow the pipe by probing every two feet until the tank is reached. Another strategy is to look for high and low spots in the yard.