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Three Types of Septic System

There are three types of septic systems permitted in Placer County. The type of system your property requires is determined by:

  • Soil quality
  • Percolation rates (how fast water flows through the soil)
  • Ground water levels

Standard Septic System i.e Gravity Flow System

The simplest system available, standard septic systems consist of:

  • Septic tank
  • Leach field

Wastewater leaves the building and enters the first compartment of the septic tank. Heavy solids form sludge in the bottom of the tank, and grease and light material form a scum layer near the top. The clear zone in between flows into the second compartment of the septic tank. The clear zone "effluent" leaves the second compartment and flows to the distribution box at the beginning of the leach field. The leach field is comprised a network of perforated pipes laid in gravel-lined trenches. The effluent is distributed to the leach lines via serial distribution.

Low Pressure Dose System

Slightly more complicated than a standard septic system, a low pressure dose septic system consists of:

  • Septic tank
  • Pump tank
  • Leach field.

Wastewater leaves the building and enters the first compartment of the septic tank. Heavy solids form sludge in the bottom of the tank, and grease and light material form a scum layer near the top. The clear zone in between flows into the second compartment of the septic tank. Effluent leaves the second compartment of the septic tank and enters the pump tank where it is stored. Effluent is pumped from here to the leach field where it is distributed evenly through a network of small diameter pipes under low pressure. Low-pressure dose systems may be utilized as an alternative for some sites to mitigate the limitations associated with poorer quality soils and slow water permeability.

Engineered or Supplemental Treatment System

The most complicated septic system, a supplemental treatment system consists of:

  • Septic tank
  • Pump tank
  • Pre-treatment media (sand filter, Advantex, Hoot)
  • Leach field

Supplemental treatment systems function like low pressure dosed systems with one major difference: after leaving the pump tank, the effluent is pre-treated prior to distribution in the leach field. Supplemental septic systems may need to be utilized for some sites to mitigate the limitations associated with shallow soil depths, soils with rapid permeability, and soils with very slow permeability.

NOTE: Supplemental treatment systems installed after January 1, 2005 fall into our Operation Maintenance and Monitoring Program and require annual maintenance by a qualified service provider. Operating permits are renewed annually after the annual maintenance have been done.

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