How Septic Tanks Work
Every sink, toilet and shower in your home drains into the septic tank. The septic tank is a watertight box usually made of pre-cast concrete or reinforced fiberglass. When solids enter the tank, (organic solid material) the paper, waste, oils and grease float to the surface, forming a layer commonly called “scum”. Over a period of time, (inorganic solid materials and the by-products of bacterial digestion) the scum deteriorates and sinks to the bottom, creating a layer commonly called “sludge”. Only clear water should exist between the scum and sludge layers and only this clear water in the middle should drain out of the septic tank and into the drain field.
There are several types of drain fields but the two most common are mineral aggregate and chambers. An aggregate drain field consists of a layer of 1 ½” rock, a perforated 4″ diameter pipe laid in a bed of rock over sandy soil. A chambered system is dome shaped with slits on the sides and open on the bottom so it sits flat in the drain field trench. As the liquid exits the tank, it spreads evenly throughout the drain field in a circuit of pipe. The liquid effluent falls from the perforated pipe and is stored in the rock bed until the sand absorbs it.
Eventually, your septic tank will have too many solids in its tank and the septic tank will need to be cleansed of those solids. Some people call this septic tank cleaning while others refer to as septic tank pumping. Regardless of how you refer to it, it is still a necessary and important step in proper septic system maintenance. If your tank is not pumped out regularly, the solids accumulate and the sludge level builds up so that it is eventually forced out into the drain field. It clogs the tiny cracks between the rocks or forms a thick layer on the bottom of the drain trench. This prevents the water from draining out of the septic tank, leading to unsanitary and unsafe conditions. Water follows the path of least resistance. When it is no longer able to exit through the drain field, it will either come up on top of the ground in your yard or it will back up in your home.
When the septic contractor goes to clean out your septic tank, it should be pumped out through the septic system’s manhole, not its smaller inspection ports. Insist on your tank being cleaned through the manhole cover and not the inspection port, as this ensures removal of all of the solids from the septic tank. Be sure that the septic tank is cleaned out completely, with nothing being left in the tank. Any solids or sludge left in the septic tank can clog the drainpipes and cause the need for very expensive repairs in the future.