After pumping, the septic tank should be rinsed with water, so that you can see the physical condition of the tank. At the end of the inspection the pumper should refill your tank with water. This will keep it from raising up if the groundwater level is high. If you have a below-ground swimming pool, you know that it could pop out of the ground if you emptied it completely. Obviously, if your septic tank is a holding tank do not refill it.