Excreta flows from the toilets to septic tank through inlet pipe and is intended to reach at the bottom of the tank by means of the inlet baffle and by its settling habits. The solid fall to the bottom forming the sludge layer and the grease, fat and lighter materials swim to the top of the tank which forms a layer called scum. In the middle there is region called clear zone and The liquid from this layer empties out into the soak well by way of the outlet pipe which is covered by an outlet baffle that keeps the scum layer away and restrict solids entering into soakage well. In conventional anaerobic septic tank if the tank is not emptied periodically it will eventually fill up until it defeats the design of the tank overcoming the protective baffle allowing the sludge layer to enter into the soak pit where it will clog the lines and porous of soil causing sewer system failure.

The septic tank in home connected with two bathroom and used by 4 to 5 people will process thousands liters of waste water every month. All of this wastewater passes through septic tank and goes to soak pit, where bacteria in the soil purify it. Soakage well normally fails because too much wastewater has been flushed into them, keeping them constantly wet and saturated. When too much water sits in the drain lines constantly, a bacterial biomat forms along the pit walls. This slimy biomat doesn't allow water to seep through it, and therefore the soil no longer can handle the wastewater. A properly designed septic system should be constructed to handle a specific amount of wastewater. This is determined by how many people are in the house.

In conventional anaerobic brick made septic tank or in any simple RCC pipe made, only about 50 percent of solids are broken down by anaerobic bacteria and the rest mount up in the bottom of Septic Tank until they are pumped out. Having too much sludge accumulated, and too much water entering the tank at once like doing several loads of washing machine in one morning and bathing water, can cause the solids to be flushed out into the soak pit where it can clog surrounding soil. Generally two types of challenges comes in case of anaerobic septic systems, one is related to Sodium in ordinary detergents, soaps, household cleaners, and water softeners cause soil particles in the soils to chemically bond. Another challenge is related to fat and grease and organic matter called the biomat. When the biomat grows too thick a waterproof barrier develops and absorption stops.

In old installations; the outlet pipe and baffle can break away allowing grease and sludge to make its way into the leach field which eventually blocks the system. These broken pipes or baffles that were designed to prevent entry are defeated and the system can no longer properly handle the waste. It is never recommended to install tanks, drainpipe, or soak pit under an area where vehicles travel. The weight of vehicle traffic can compress soil, and crush plastic, cover of septic tank or drain pipes. When solids build up in septic tank through overuse they can overflow into the soaking area and clog drain pipes and soil. It is never a good idea to plant trees near sewer system because their roots may reach into soil and eventually into drain pipes.