Most septic tanks in this area have two lids – one over the inlet pipe, one over the outlet pipe. Usually they are about 20 to 24 in square for concrete tanks, or round for plastic tanks.
This can vary depending on age and type of tank – some will have one lid, some will have lids in different places, etc.
For standard tanks, the best practice is to pump from both the inlet and the outlet side. In modern tanks, the inlet side is about 2/3 of the tank. The inlet side should have most of the solids, but there is usually some solids on the outlet side and these should be removed to make sure they don’t clog the filter or travel into the drainfield. The filter (if there is one) should also be cleaned by being removing it from the outlet tee and held over the inlet side while being rinsed with a hose. (See this section for information about uncovering tanks.)