A septic tank is merely a large cement tank that sits in the ground. When sewage from the house enters the septic tank, the heavy solid material goes to the bottom, where it decomposes. The light fluid material remains at the top and overflows through a pipe to a leech bed, where the water is dispersed. Because this fluid contains very tiny particles of sewage, the area where the sewage is dispersed becomes saturated and will no longer accept any more liquid (over a period of 15 or 20 years). When this happens, the septic tank backs up. A backed up septic tank may prevent the homeowner from flushing his/her toilet or may flood the yard.
Most new septic systems in our area must be replaced with a mound system. A mound system contains a leech bed that sits on top of the normal soil. The leech bed, or mound, is made up of sand which allows a great deal of water saturation and penetration. The reason mound systems are used is because the sand that is brought in to build the mound is more absorptive than natural soils. Mound systems are significantly more expensive than normal septic systems as a large quantity of special soil must be brought in to construct a mound. Mound systems are easier to replace because the mound is simply replaced when it becomes saturated with particles.