The inlet to the distribution box should be at least 1 inch above the outlets. You can purchase a precast distribution box with your septic tank. Investigate all areas of the lot either higher or lower than your house to find the best absorption field location. Locate the absorption field where good grass cover is possible. Do not locate it near trees or shrubs.
Suitable soil is necessary for successful treatment of septic tank effluent.
A suitable soil texture has a percolation rate between 5 and 60 minutes per inch. Clay loam or clay soils are not suitable as sewage will not flow through them at an adequate rate. Very coarse-textured soils, sands or gravel are also not suitable because sewage flows through them too rapidly to be filtered properly. Bacteria may reach the ground water table if sewage is applied to coarse soil. Keep in mind that a water table or bedrock within 4 feet of the trench bottom will keep the absorption field from working properly.