Flush the toilet, take a shower, wash the dishes and all the water goes from the faucet (or tank) straight in to the septic system. When the water enters the septic system, a septic drain field or leach field, is used to remove the contaminants and impurities from the liquid that comes from the septic tank.
The leach field is essentially the disposal ground for organic materials that will be broken down by the microbial ecosystem. The leach field is typically an arrangement of trenches with pipes and porous materials – usually gravel – that is then covered by soil to keep animals out and surface water in.
How big a leach field should be is determined by the nature of the soil that the leach field is constructed in, what – if any – seasonal changes are present in the level of groundwater, how much water must be absorbed by the leach field in a given day and the rate at which the water is absorbed.
Since the water that flows into the leach field must be absorbed by the surrounding soil, the percolation rate – or how fast absorption occurs – must be known. The absorption rate is expressed as minutes per inch.
Natural fluctuation in groundwater levels must also be considered, since the bottom of the leach field trenches must be at least four feet above the ground water level. Consulting a professional septic system installer is the best option for this determination since a slow percolation rate does not allow for a standard leach field in the soil.
The amount of water absorbed each day is expressed as gallons per day, per bedroom. The consensus is 150 gallons per day per bedroom for houses built before 1979, whereas newer homes with water-restricted toilets and faucets must allow for 130 gallons per day. The required flow rate is determined by multiplying the appropriate flow (150 or 130 gallons per day) by the number of bedrooms in the home. That figured, combined with the absorption rate, is used to determine the size of the leach field required.
For more information on septic systems, septic tanks and leach fields, contact the experts at Soils and Environmental Services. Serving the Northern Virginia and Washington DC residential and commercial markets since 1987, Soils and Environmental Services, Inc. specializes in designing alternative septic systems and assessing septic tank options for homes, commercial properties, and sub-divisions.