Raw sewage (black water) flows from the house to the first of 2 septic tanks. The weighs are trapped in this tank where they brake down. Once the liquid drains 2 a 2nd tank and some heavies or sediment was able to leave the first tank the 2nd tank catches it. When the liquid leaves the 2nd tank its now call gray water ready to the drain field.
When entering the drain field the gray water runs through the lateral pipe to each of the drain beds equally. Each bed has 4″ pipes with about 2 -1″ holes every 6” allowing the gray water to spread into the river rock. Where the drain field does its work is not in the rock but on the edge of the rocks and the meeting of the sand a 1/8″ membrane is formed that eats the bacteria out of the water.
Once your drain field is installed do not hurt or damage the edges of the sand and rock bed of your drain field.