SEWAGE SYSTEM WORKSHEET - 4 INCH LEACHING TILE
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
; 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.