Septic Components - Leach Lines
Leach Lines with Perforated Pipe:
Leach lines are trenches that are filled with washed rock/gravel to flow level. Perforated pipe lays on top of the rock at a level grade. More rock is added to cover the pipe, and paper or other approved filter material is used to keep soil from filtering down into the rock. The paper does deteriorate, but by the time it does the soil is compacted enough to prevent it from dropping into the rock. Perforated leach lines are usually the first choice for a standard individual sewage disposal system design. The pipes of an approved material and are pre-drilled to allow the effluent to trickle through the gravel for treatment. The lines are also shallow enough (12" to grade) for some aerobic bacteria breakdown and some evapo-transpiration.
Cross-section of a leach line.
The area of an individual sewage disposal system's disposal field is sized based on the proposed sewage flow and the soil's percolation rate.
Individual sewage disposal systems are designed to accommodate a sewage flow of 350 gallons per day plus 150 gallons for each additional bedroom.
A standard leach line is considered to be three (3) feet wide and three (3) feet deep with a length as required. A non-standard leach line is wider, narrower, and/or deeper than three (3) feet with a length as required.
Some El Dorado County requirements for standard leach line installation:
- Maximum length of each line 100 ft.
- Minimum spacing of lines, center-to-center = 10 ft.
- Minimum depth of natural earth over all lines as measured from the lowest point of natural grade 12 in.
- Maximum "drop" in leach line (bottom of trench and drain pipe) 3 in./100'
- Drain line pipe ends must be capped, holes in pipe must face downward
- A minimum of one observation/inspection riser (see: Septic Components: Inspection Riser) shall be installed at the, end of each trench.
- Drain rock/gravel shall be clean, sound gravel or crushed rock ranging in size from 3/4 to 1 1/2inch diameter, with <5% outside this range.
Gravel-less Leach Lines:
Gravel-less trench construction (e.g., Infiltrator® systems) may be utilized instead of drain rock in the disposal trench. The design, manufacturing, and materials used shall be durable and acceptable to the Department.
A single Infiltrator chamber with an end cap.
Some El Dorado County requirements specifically for gravel-less leach line installation:
- Maximum length of each line 100 ft.
- Minimum spacing of lines, center-to-center = 10 ft.
- Minimum depth of natural earth over all lines as measured from the lowest point of natural grade 12 in.
- "Drop" in leach line (bottom of trench and chambers) shall be as level as possible - max. 3 in/100 ft.
- A minimum of one observation/inspection riser (see: Septic Components: Inspection Riser) shall be installed at the, end of each trench.
- Scarify (scratch) the trench sidewalls to prevent smearing prior to chamber installation.
- Provide a splash guard under the pipe inlet to prevent divets in the trench bottom.
Installation of gravel-less leach line chambers.