By Tony Lawson,2015-03-31 20:43
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    1. Basic Requirements/ Table of Specifications:

    Number of Bedrooms Size of Septic Tank Soil Permeability/Total Leaching

    in dwelling in gallons Slight Moderate Severe

     1-2 1000 300 460 600+

    3 1500 460 600 900+

    4 2000 600 800 1200+

2. Minimum Distances Required From Sewage System:

    ; 10 ft. from any property line

    ; 10 ft. from any dwelling

    ; 10 ft. from any water supply line

    ; 10 ft. from any right-of-way line or driveway

    ; 8 ft. from any drainage line

    ; 50 ft. from any potable water supply

3. Septic Tank Requirements:

    ; Building sewer has minimum diameter of 4 inches with schedule 40 rating.

    ; Fall of sewer pipe from residence to tank joints - recommend 1/8* inch per foot of sewer

    line. Sewer line laid in good alignment with tank joints - no 90 degree angles.

    ; Tank is level in ground.

    ; Inlet and outlet baffles to be in place and in good repair.

    ; Inlet and outlet of tank are to be sealed.

    ; Outlet pipe must have a minimum diameter of 4 inches with schedule 40 rating.

    ; Septic tank is to be equipped with 2 risers extended to grade. Risers must be placed over

    inlet and outlet inspection ports on tank and sealed for a watertight connection.

    ; An effluent filter on outlet pipe of all septic tanks.

    ; A watertight test on all tanks with or in series with pump chambers.

    4. Leaching Field Requirements:

    ; Proper amount of lineal leaching installed according to soil conditions.

    ; Leaching system is to be divided into two equal and alternating fields.

    ; Distribution box installed with level outlets, shut off valve, an extended to grade.

    ; Outlet pipes from distribution box are to be solid for at least 5 feet with no gravel within 5

    feet of the box.

    ; Minimum distance between leaching lines shall be 6 feet. Minimum distance between a

    leaching line and a perimeter or curtain drain shall be 8 feet.

    ; Maximum length of any leaching line shall be 150 feet.

    ; A leaching trench shall have a minimum width of 12 inches unless permission is given

    for less.

    ; Depth of any leaching trench shall be a maximum of 30 inches, and a minimum of 18

    inches. In most cases, leaching trenches shall be installed at a depth of 18 to 20 inches


    ; Drop boxes or earthen dams are to be utilized whenever a leaching line exceeds 6 inches of

    fall in 100 feet of leaching line. Earthen dams are to be constructed of undisturbed natural

    soil and the leaching pipe must be damned or elevated at least 2 inches and no more than 4

    inches to be considered an effective dam. The dam is to be of a minimum of 24 inches in

    length and no gravel is to be placed on the dam. The dam itself shall be solid pipe.

    ; Minimum diameter of leaching pipe is 4 inches.

    ; Fall of any leaching line is no greater than 3 inches for every 50 feet.

    ; Minimum of 12 inches washed gravel or stone (3/4 inch to 1 1/2 inch) in leaching,

    extending 6 inches below and 2 inches above pipe.

    ; Gravel shall be covered with a 2-inch layer of hay, straw, or similar material before

    covering with earth.

    ; A minimum earthen cover of 6 inches is required. It is recommended that the cover

    over the lines be extended an additional 4 to 6 inches to allow for settling.

    5. Curtain Drain Requirements:

    ; A curtain drain is to be constructed out of 4-inch perforated drainage tile.

    ; The curtain drain must be placed at a minimum depth of 6 inches below the bottom of

    the leaching trenches.

    ; The trench must contain at least 12 inches of gravel. In some cases, gravel is to extend

    to the surface of the trench.

    ; Minimum distance between a leach line and a curtain drain shall be 8 feet.

    ; The outlet of the curtain drain must be constructed out of 4-inch schedule 40 PVC

    with a minimum length of 10 feet.

    ; An animal guard must be installed on the curtain drain outlet.

    6. Curtain Drain Terminology:

    ; Perimeter drain: subsurface drains installed around the perimeter of absorption Fields

    designed to lower the high water table. A perimeter drain is required on soils where a

    seasonal high water table is 4 feet of less from the ground surface. It must be determined if

    an adequate outlet exists for the perimeter drain before the septic permit is approved.

    ; Full curtain drain: same as above, but due to a large absorption field system, this is an

    additional drainage line installed between the split septic fields providing additional

    subsurface drainage for slow permeability soils.

    ; Interceptor drains: subsurface drains installed on the up-slope side of leaching tile fields to

    intercept surface water before it reaches the area of the leaching field.

    * For specifications on pretreatment devices or experimental systems, please contact our office.

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