HOW SEPTIC SYSTEMS WORK

Most Septic Systems are comprised of four parts:

1. The Home and it’s plumbing
2. A Septic Tank
3. The Drain Field (or Leach Field)
4. The Soil and Bedrock beneath

The Home – Where it all begins:
All of your home’s plumbing fixtures feed into a main drain pipe that leaves your home and enters the septic tank.  These fixtures can include kitchen sinks, dishwashers, garbage disposals, bathroom toilets, bathroom sinks, bathtubs and showers, washing machines, utility sinks, and other household fixtures and drains.  Whatever you allow to enter a drain or water fixture in your home will end up in your septic tank.

The Septic Tank – The heart of your septic system:
The septic tank holds the waste that leaves your home via the main drain pipe. This tank is often made of concrete and is buried in the ground near the home.  The size of the septic tank installed in your system is based on the amount of waste it is expected to process. Local building codes will often specify the volume of the septic tank by number of bedrooms, or occupancy of a structure.  A four bedroom household of five people will require a larger septic tank than that of a small two bedroom home.

All raw liquid or solid household waste moves by gravity to the septic tank where the flow is slowed to allow the waste treatment process to begin.  Once in the tank, the waste is allowed to stand and separate into three layers over a period of about three to five days.  The heavy solids settle to the bottom of the tank as sludge, a large middle layer of liquid effluent, and a top layer of floating oil, grease and light solids called scum.  During this holding period in the septic tank, billions of anaerobic (without air) enzymes and bacteria work to digest and convert the scum and sludge into liquefied waste.  As more waste water enters the tank from the home, the liquid effluent is forced from the tank and into the next component of the septic system, the drain field.  A sanitary tee pipe and baffles in the tank prevent solids from flowing out with the liquid effluent into the drain field.

The Drain Field (or Leach Field) – An active septic system filter:
A septic drain field is essentially a group of long, perforated pipes that are installed in gravel filled trenches buried a few feet beneath the topsoil. This system of drain pipes carry the cloudy liquid effluent from the septic tank and allow it to slowly trickle out through the gravel trenches and into the ground.  As the effluent flows through the drain (leach) field, a new group of aerobic (with air) enzymes and bacteria begin to further break down the liquid into nutrients and base elements. Over time, a healthy layer of microbe filled bio material forms in the bottom of the trench, acting as another filter of germs and other pollutants for the liquid effluent.

The Soil – The final filter:
The purpose of the septic system’s drain field is to deliver the waste water to the soil where the final treatment process occurs. The soil filters the effluent while more oxygen dependent (aerobic) enzymes and bacterial action further break down chemicals and germs. If the system contains too much water or liquid, the good enzymes and bacteria will not have enough oxygen to effectively work, and the septic system may clog.  In the soil the remaining liquid dissipates through evaporation into the atmosphere and, by filtration, further into the ground before it enters the water supply. 

A Recap of the Sewage Treatment Process:

1. Solid and liquid waste is allowed to stand in septic tank for 3-5 days.  Scum (Oil & Grease) floats and solids settle into Sludge. 
2. Enzymes & bacteria break down the settled solids turning it into liquid, called “liquid effluent”.
3. Liquid effluent flows to the drain field (or leach field) and seeps into the surrounding soil.
4. The soil treats effluent and removes harmful bacteria, viruses, and nutrients.  (Bacteria and enzymes in soil break down & remove most contaminants from wastewater before it reaches groundwater)

Questions? Call the Toll-Free Helpline 1-800-613-4242