About this chapter: Chapter 6 covers the design of 'conventional' soil absorption systems. These systems are conventional in the sense that nonpotable water from the outlet of a septic tank flows by gravity into a piping network for distributing the water in an excavated area nearby. The piping is backfilled with the finished grade blending into adjacent grade level.
The provisions of this chapter shall govern the sizing and installation of soil absorption systems.
The bottom area for seepage trenches or beds or the sidewall area for seepage pits required for a soil absorption system serving residential property shall be determined from Table 603.1 using soil percolation test data and type of construction.
MINIMUM ABSORPTION AREA FOR ONE- AND TWO-FAMILY DWELLINGS
required for water
to fall 1 inch)
PITS (square feet
(square feet per
|1||0 to less than 10||165||205|
|2||10 to less than 30||250||315|
|3||30 to less than 45||300||375|
|4||45 to 60||330||415|
For SI: 1 minute per inch = 2.4 s/mm, 1 square foot = 0.0929 m2.
The minimum required soil absorption system area for all occupancies, except one- and two-family dwellings, shall be based on building usage, the percolation rate and system design in accordance with Tables 604.1(1) and 604.1(2). The minimum soil absorption area shall be calculated by the following equation:
A = Minimum system absorption area.
AA = Absorption area from Table 604.1(1).
CF = Conversion factor from Table 604.1(2).
U = Number of units.
MINIMUM ABSORPTION AREA FOR OTHER THAN ONE- AND TWO-FAMILY DWELLINGS
(minutes required for
water to fall 1 inch)
feet per unit)
|1||0 to less than 10||110||140|
|2||10 to less than 30||165||205|
|3||30 to less than 45||220||250|
|4||45 to 60||220||280|
For SI: 1 minute per inch = 2.4 s/mm, 1 square foot = 0.0929 m2.
|Apartment building||1 per bedroom||1.5|
|Assembly hall—no kitchen||1 per person||0.02|
|Auto washer (service buildings, etc.)||1 per machine||6.0|
|Bar and cocktail lounge||1 per patron space||0.2|
|Beauty salon||1 per station||2.4|
|Bowling center||1 per bowling lane||2.5|
|Bowling center with bar||1 per bowling lane||4.5|
|Camp, day and night||1 per person||0.45|
|Camp, day use only||1 per person||0.2|
|Campground and camping resort||1 per camping space||0.9|
|Campground and sanitary dump station||1 per camping space||0.085|
|Car wash||1 per car||1.0|
|Catch basin—garages, motor-fuel-dispensing facility, etc.||1 per basin||2.0|
|Catch basin—truck wash||1 per truck||5.0|
|Church—no kitchen||1 per person||0.04|
|Church—with kitchen||1 per person||0.09|
|Condominium||1 per bedroom||1.5|
|Dance hall||1 per person||0.06|
|Dining hall—kitchen and toilet||1 per meal served||0.2|
|Dining hall—kitchen and toilet waste with dishwasher or food waste grinder or both||1 per meal served||0.25|
|Dining hall—kitchen only||1 per meal served||0.06|
|Drive-in restaurant, inside seating||1 per seat||0.3|
|Drive-in restaurant, without inside seating||1 per car space||0.3|
|Drive-in theater||1 per car space||0.1|
|Employees—in all buildings||1 per person||0.4|
|Floor drain||1 per drain||1.0|
|Hospital||1 per bed space||2.0|
|Hotel or motel and tourist rooming house||1 per room||0.9|
|Labor camp—central bathhouse||1 per employee||0.25|
|Medical office buildings, clinics and dental offices|
Doctors, nurses and medical staffOffice personnel
1 per person1 per person
1 per person
|Mobile home park||1 per mobile home site||3.0|
|Motor-fuel-dispensing facility||1 per car served||0.15|
|Nursing or group homes||1 per bed space||1.0|
|Outdoor sports facility—toilet waste only||1 per person||0.35|
|Park—showers and toilets||1 per acre||8.0|
|Park—toilet waste only||1 per acre||4.0|
|Restaurant—dishwasher or food waste grinder or both||1 per seating space||0.15|
|Restaurant—kitchen and toilet||1 per seating space||0.6|
|Restaurant—kitchen waste only||1 per seating space||0.18|
|Restaurant—toilet waste only||1 per seating space||0.42|
|Restaurant—(24-hour) kitchen and toilet||1 per seating space||1.2|
|Restaurant—(24-hour) with dishwasher or food waste grinder or both||1 per seating space||1.5|
|Retail store||1 per customer||0.03|
|School—meals and showers||1 per classroom||8.0|
|School—meals served or showers||1 per classroom||6.7|
|School—no meals, no showers||1 per classroom||5.0|
|Self-service laundry—toilet waste only||1 per machine||1.0|
|Showers—public||1 per shower||0.3|
|Swimming pool bathhouse||1 per person||0.2|
A seepage pit shall have not less than an inside diameter of 5 feet (1524 mm) and shall consist of a chamber walled-up with material, such as perforated precast concrete ring, concrete block, brick or other approved material allowing effluent to percolate into the surrounding soil. The pit bottom shall be left open to the soil. Aggregate of 1/2 inch to 21/2 inches (12.7 mm to 64 mm) in size shall be placed into a 6-inch minimum (152 mm) annular space separating the outside wall of the chamber and sidewall excavation. The depth of the annular space shall be measured from the inlet pipe to the bottom of the chamber. Each seepage pit shall be provided with a 24-inch (610 mm) manhole extending to within 56 inches (1422 mm) of the ground surface and a 4-inch-diameter (102 mm) fresh air inlet. Seepage pits shall be located not less than 5 feet (1524 mm) apart. Excavation and scarifying shall be in accordance with Section 605.4. The effective area of a seepage pit shall be the vertical wall area of the walled-up chamber for the depth below the inlet for all strata in which the percolation rates are less than 30 minutes per inch (70 s/mm). The 6-inch (152 mm) annular opening outside the vertical wall area is permitted to be included for determining the effective area. Table 605.3, or an approved method, shall be used for determining the effective sidewall area of circular seepage pits.
EFFECTIVE SQUARE-FOOT ABSORPTION AREA FOR SEEPAGE PITS
|INSIDE DIAMETER OF|
IN FEET PLUS 1 FOOT FOR
WALL THICKNESS PLUS 1
FOOT FOR ANNULAR SPACE
|DEPTH IN FEET OF PERMEABLE|
STRATA BELOW INLET
For SI: 1 foot = 304.8 mm.
Observation pipes shall be provided. Such pipes shall be not less than 4 inches (102 mm) in diameter, not less than 12 inches (305 mm) above final grade and shall terminate with an approved vent cap.
The bottom 12 inches (305 mm) of the observation pipe shall be perforated and extend to the bottom of the aggregate. Observation pipes shall be located not less than 25 feet (7620 mm) from any window, door or air intake of any building used for human occupancy. Not more than four distribution pipelines shall be served by one common 4-inch (102 mm) observation pipe where interconnected by a common header pipe (see Appendix-A, Figure A-4).
Exception: Where approved and where the location of the observation pipe is permanently recorded, the observation pipe shall be not more than 2 inches (51 mm) below the finished grade.