How a Septic System Works

A septic system is your property’s on-site waste management system.  Often forgotten, they are quickly centerstage when not functioning or failing.  So, what is a septic system and how do they work? Read on for an overview of a typical septic system.

A typical septic system in northeastern Nebraska is comprised of four different components:  the building drain (sewer), a septic tank, distribution system, and the leach field.  Your septic system takes in a combination of waste products from the building and turns them into:  clean water, inorganic solids, gasses, and insoluble oils & grease.


The sewer/building drain’s function is simple; get the waste from your home or building to the tank without inhibiting flow or filtering/processing the waste stream in anyway.  This is true for any sewer or drain line whether dumping to a septic or a municipal sewer.

The waste exits the drain and enters the septic tank through the inlet baffle.  The baffle serves merely as a means to divert the flow and reduce the velocity of waste entering the tank.  The baffle prevents cross tank washing or stirring of the tank’s contents.  Waste is diverted down to the lower third of the tank.

Your septic tank accounts for about 50% of the waste processing but must be able to retain 100% of the inorganic solids and insoluble oils/grease.  The tank uses enzymes and bacteria to process waste.  Once that waste enters the tank, enzymes break down organic solids into simple blocks of protein, carbohydrates and fats.  Once broken down into these simple forms they are more easily digested by bacteria.  The bacteria consume these blocks and in turn excrete water, inorganic solids, insoluble oils/grease and different gasses (carbon dioxide, methane, hydrogen sulfide, to name a few).

Inside the septic tank the waste forms three layers.  The top “scum” layer, middle “clear” layer, and the bottom “sludge” layer.  Our bacteria reside in the “clear layer” of the tank.  This is the middle portion made up of oxygenated water.  The insoluble oils sit on top forming the “scum” layer, while the inorganic and heavy solids settle to the bottom to form the “sludge” layer.  Little happens bacteriologically in the scum & sludge layers.


For every gallon of waste & water that enters the tank there must also be a gallon exiting the tank.  The septic tank should always be “full” meaning it is at the proper operating level.  If that level raises or lowers this indicates an issue in the system.

Refined waste water or effluent exits the tank via the outlet baffle.  This baffle only allows the middle “clear” water layer of the tank to exit.  No solids or insoluble oils/grease should leave the septic tank.  The effluent exits the tank and enters the distribution system.  Distribution can be a pumping chamber, distribution box, header pipe manifold, or simply a single pipe leading to the leach fields/trenches.

Effluent flowing through the distribution system is supposed to be balanced and evenly distributed to the leach trenches.  We have found a distribution box is the best method to send equal amount to each leach trench.

Leach fields in our areas of Nebraska, mainly Boone, Nance, Platte, Antelope and Madison counties are primarily constructed in one of two ways.  Older systems use a perforated pipe and gravel leach system while newer systems utilize gravelless chambers.  Both are constructed in a trench 2-3’ wide.  A gravel and perforated pipe system has a pipe with holes or slots cut in it completely surrounded by gravel.  Gravelless chambers are sections of arches that when laid form a semi-circle tube with a dirt bottom.

A third method, we prefer to use, is a perforated pipe suspended in gravelless chambers. Using a perforated pipe down the length of the trench in chambers, allows future leach field servicing and cleaning, if needed.  We find it impossible to service and clean standard gravelless chambers.

All these types of leach systems function in the same way.  Effluent exits the distribution system and enters the leach system where it comes in contact with gravel or natural soils.  The effluent is still bacteriologically active meaning the water contains remnant particles of proteins, sugars, fats, etc along with the bacteria that is feeding on them.  When this mixture splashes down on gravel or soil it leaves its saturated state and enters a highly aerobic (oxygenated) state as it’s no longer surrounded by water but still wet and exposed to air.  Leach fields cannot have more than four feet of soil cover in order to provide oxygen from the surface getting down through the soil for the bacteria.

This is where the final waste processing takes place.  In the leach field, the bacteria are voracious, consuming effluent at a rapid rate due to the amount of air and surface area present in the soil.  They completely process the waste leaving nothing behind but clean, but turbid, water off-gasses which rise up through the soil, and minute amounts of inorganic solids and insoluble oils/grease which are caught by the soils.

The complete system when designed, installed and maintained properly will function perfectly for years and result in zero pollution or disruption to the building it serves.

Issues can arise from several factors, including:

  • A tank or leach field that is too small. The leach field becomes overwhelmed with effluent that has too high of organic load.  The bacteria cannot work efficiently or quickly enough to process the waste. An undersized system results in ground water pollution, or when severe, ponding and building backups.
  • Routine pumping and maintenance is not performed to remove the inorganic solids and insoluble oils/grease from the tank. These trapped wastes can overload the tank and begin to flow into the leach fields.  These will “silt in” the gravel or soil effectively filling all the voids and not allow water to percolate down through the soil, resulting in surface ponding or backups in the building.

The easiest way to maintain a septic system is by having routine pumping and service performed by a license, trained and knowledgeable provider, like the team at Speed Services.  By keeping the inorganic levels in the tank low, we can prevent leach field failure.  Even if the system is failing or have been compromised our staff has developed innovative solutions to regain some of that capacity and prolong the life of an aging system.

We’re also available for the design and installation process of creating a new system, replacing a failed system or system modification.  Our years of experience in servicing and rejuvenating septic systems has given us a lot of insight on how to design and install a long lasting, robust, and easy to maintain system.  From design & installation to service and maintenance, the team at Speed Services is one you can rely on for the best in septic system services.  Give us a call at 1-844-DRAIN-01 or click here to request service for your septic today!

Author: jonporter


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