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Septic Systems

What Are Septic Systems?
  • A typical septic system consists of a septic tank and a drainfield (or soil absorption field).

  • The septic tank digests organic matter and separates floatable matter (e.g., oils and grease) and solids from the wastewater. In conventional, or soil-based systems, the liquid (known as effluent) is discharged from the septic tank into a series of perforated pipes buried in a leach field, chambers, or other special units designed to slowly release the effluent into the soil. This area is known as the drainfield.

  • Alternative systems use pumps or gravity to help septic tank effluent trickle through sand, organic matter (e.g., peat and sawdust), constructed wetlands, or other media to remove or neutralize pollutants like disease-causing pathogens, nitrogen, phosphorus and other contaminants. Some alternative systems are designed to evaporate wastewater or disinfect it before it is discharged to the soil.

How a typical conventional septic system works:
  • All water runs out of your house from one main drainage pipe into a septic tank.

  • The septic tank is a buried, water-tight container usually made of concrete, fiberglass, or polyethylene. Its job is to hold the wastewater long enough to allow solids to settle down to the bottom forming sludge, while the oil and grease floats to the top as scum. Compartments and a T-shaped outlet prevent the sludge and scum from leaving the tank and traveling into the drainfield area.

  • The liquid wastewater (effluent) then exits the tank into the drainfield.

  • The drainfield is a shallow, covered, excavation made in unsaturated soil. Pretreated wastewater is discharged through piping onto porous surfaces that allow wastewater to filter through the soil. The soil accepts, treats, and disperses wastewater as it percolates through the soil, ultimately discharging to groundwater. If the drainfield is overloaded with too much liquid, it can flood, causing sewage to flow to the ground surface or create backups in toilets and sinks.

  • Finally, the wastewater percolates into the soil, naturally removing harmful coliform bacteria, viruses and nutrients. Coliform bacteria predominantly inhabits the intestines of humans or other warm-blooded animals. It is an indicator of human fecal contamination.

  • View an animated, interactive model of how a household septic system works created by the Guadalupe-Blanco River Authority.

Understanding Your Septic System is Important!
  • According to the Maine DEP, properly functioning septic systems are not likely to contribute large amounts of phosphorus to China Lake.  However, as few as 1 or 2 failing septic systems can have an outsized, adverse effect on our water quality.

  • Pre-1971 properties can have cesspools or undersized drain fields, and may be located very close to the lake. These cesspools and undersized drain fields lack the ability to filter waste, so sewage contaminates the surrounding soil and seeps into the lake.  

  • There are some additional cases when you will want to pay careful attention to how your septic system functions: 

    • Systems in the shoreland zone that are sited over fractured bedrock with only minimal depth of soil between the bottom of the system and the bedrock

    • Systems that are sited close to the lake on coarse sand and gravel

    • Systems that are sited close to the lake and were installed before the 1971 Mandatory Shoreland Zoning Act.

Additional Resources
  • China Land Use Ordinance: Chapter 2 (11/8/22)
    Septic systems are regulated under this ordinance. All new septic systems must comply with the State of Maine Subsurface Wastewater Disposal Rules and local requirements. Systems must be no closer than 100 ft from the high-water line of a waterbody and must be located in suitable soils where there have been at least five observation holes dug. Clearing of woody vegetation for septic installation China Lake must not extend closer than 100 feet from the shoreline of any waterbody or wetland. The use of holding tanks is also prohibited for new residential developments. 


  • Septic Tank Contractors (BBB) near China Village, ME. This list is for informational purposes only, and is not an endorsement from China Village or its Code Enforcement Officer.

  • Best practices for septic systems, by David Rocque, 1999


Masthead Photo Credit: Jen Syer

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