The septic distribution box is part of the conventional drain field system. It distributes the effluent (wastewater) evenly to the drain field (leach field).
The most common way to make this work is through the use of gravity.
Since water flows downhill, placing the box so that the water will flow into it from the tank and then on into the drain field requires only this common-sense knowledge (and perhaps the ability to shoot grades with a surveyor’s stick).
As effluent flows out of the tank, it travels a short distance into the septic distribution box. The box, which comes in many shapes and sizes, handles the effluent by sending the wastewater into various drainfield lines or trenches.
A septic distribution box is a concrete or plastic structure that has a number of openings. Septic pipes fit into the openings, usually with the help of a gasket. The distribution box has a cover because it will be buried under ground. For this reason, concrete distribution boxes tend to work better than other kinds, because the construction is sturdier. Also, a concrete distribution box is easier to find (a probe rod can locate it) and inspect.
The distribution box openings can be fitted with flow leveling devices that rotate so that some openings are higher or lower than others. This is to ensure that all of the drain field lines are receiving the same amount of effluent waste.
It is important for the distribution box to work properly. An improperly working septic distribution box is a main reason for drainfield failure. The equal distribution of the wastewater will maximize the life of the drain field and the entire septic system.
An alternate distribution method uses pipes instead of a box to send wastewater into the drain field. In using this method, watertight pipes lead to the trenches in the drainfield.
HOW YOUR SEPTIC TANK WORKS
•Concrete septic tanks are the most common type of septic system. They allow higher effluent levels than other types of septic tanks and their weight keeps them from floating within the ground when they are full, unlike plastic tanks. Because of the concrete material used in their construction, they tend to have a longer lifetime. All of those factors have made concrete septic tanks approved for use in many countries.
Waste Flows In
•Concrete septic tanks work using one or two compartments. Waste enters the tank from toilets, sinks and pipes, which connect to an underground system of pipes leading to the tank. Septic tanks are home to bacteria that decompose biological waste. An intake pipe allows waste to enter the tank slowly using flaps. This is necessary to keep disturbance to the sludge in the bottom of the tank to a minimum. Sludge is the undigested components of the waste. The digested waste is turned into water and gases, which are discharged into a leach field outside of the septic tank using an outlet pipe.
•Most septic tanks are buried 10 feet away from the building they service and are buried one foot below the surface of the ground. This allows them to be pumped out and maintained by a service professional. Sludge should be cleaned out of concrete septic tanks every two to four years. If it is not removed regularly, it can lead to failure of the septic tank. However, with proper care and inspection, most concrete septic tanks should last a lifetime.
A leach field consists of a series of four-inch diameter perforated distribution pipelines placed in two-to-three foot wide trenches. The perforated pipe is placed on top of gravel which is also used to backfill around the pipe. The gravel promotes drainage and reduces root growth near the pipeline. Untreated building paper or straw is placed over the gravel to prevent fine soil particles from migrating into the gravel. The building paper or straw does not reduce the evapotranspiration of the wastewater. A minimum topsoil cover is placed over the gravel to protect the leach field, prevent contact with the wastewater and reduce infiltration from rain and snow.
Effluent from the septic tank flows by gravity or is pumped to a leach field for disposal. The wastewater effluent is absorbed by soil particles and moves both horizontally and vertically through the soil pores. The dissolved organic material in the effluent is removed by bacteria which live in the top ten feet of the soil. As the effluent moves through the soil, the temperature and chemical characteristics of the wastewater change and create an unfavorable habitat for most bacteria and viruses. Therefore, as the septic tank effluent moves through the soil, organic material and microorganisms are removed. The wastewater generally percolates downward through soil and eventually enters a groundwater aquifer. A portion of the wastewater moves upwards by capillary action and is removed at the ground surface by evaporation and transpiration of plants.