The concrete, plastic, fiberglass or sometimes steel (older style) septic tank is buried in the ground, usually a minimum of 10 feet from the house. The top of the tank is usually about 8″-24″ below the soil surface so it can be periodically opened for inspection and pumping. The septic cover or lid access for service & pumping is approx 18″ round or square up to 24″x48″, the tank size is approx 8’x6’x6′. The 4″ pipe vent that sticks through the ground is not access for service or pumping & only serves as a vent & a locator for your septic tank. If you do not know for sure where the tank is located, locate where the house sewer pipe leaves the house. In a house with a basement, this is where the pipe passes through the wall. Locating the exit point may be more difficult for a house with no basement. If the pipe exit can be found, the tank normally begins about 10 feet from the house outside wall and in line with the house sewer pipe. If the soil is not frozen, the tank can be located by pushing a slender metal rod into the ground until it hits the buried tank. An inexpensive metal rod about 1/8 inch in diameter for can be purchased at most hardware stores. Be careful when probing for the tank and avoid hammering the metal rod into the ground – you could break a sewer pipe.