Current through Register Vol. 48, No. 12, March 22, 2024
a) Septic Tank
Approval. Manufacturers of prefabricated septic tanks shall submit a set of
plans for each size and configuration of septic tank to the Department for
approval. Plans shall be drawn to scale and show all dimensions, baffles, tees,
cleanouts and material specifications. The Department will provide a written
approval for each size tank when the plans are found to conform to the
requirements of this Part.
1) The Department
will issue an approval number to each manufacturer for each series of approved
septic tanks and will maintain a listing of the approved manufacturers and
approved septic tank series.
2) No
prefabricated septic tank shall be sold, offered for sale, or installed other
than those which have been approved by the Department. The tank shall bear the
manufacturer's approval number and the liquid capacity of the tank, in gallons,
prominently displayed on the outside end wall of the tank above, or next to,
the outlet pipe so that this information is readily visible after installation
and prior to covering. The Illinois Department of Public Health approval number
shall not be used on any tank other than the septic tank for which it is has
been issued.
3) All persons who
manufacture, sell, offer for sale or deliver septic tanks or aerobic treatment
plants in or into the State of Illinois shall record the following information
about each septic tank or aerobic treatment plant sold or delivered. This
information shall be available for inspection by the Department or local
authority upon request.
A) Name of purchaser
or property owner (if different);
B) Location of delivery (county and address,
legal description or driving directions);
C) Date of sale and delivery; and
D) Size of septic tank or model of aerobic
unit.
b)
Septic Tank Construction. Septic tanks shall be designed and constructed in
accordance with the following: (Appendix A, Illustration E is an illustration
of these requirements.)
1) A septic tank shall
be watertight and constructed of sound and durable materials not subject to
excessive corrosion, decay, frost damage or cracking due to settling or
backfilling.
2) Engineering
Specifications
A) The tank shall support a
top-dead load of not less than 500 pounds per square foot, and concrete tanks
shall have a minimum 28-day compressive strength of 3000 pounds per square inch
(psi).
B) Tanks shall be designed
and constructed so that they will not collapse or rupture when subjected to
anticipated earth and hydrostatic pressures when the tanks are either full or
empty. The manufacturer, design engineer or structural engineer shall certify
in writing to the Department that the tank is designed and constructed to meet
the load requirements of this Part. If additional loading is anticipated, the
tank shall be strengthened to accommodate the additional loading.
3) Materials. Septic tanks shall
be constructed of any of the following approved materials:
A) Poured-in-place reinforced
concrete.
B) Precast reinforced
concrete.
C) Concrete block,
provided that the core is filled with concrete and reinforcing rods are
inserted in the core prior to pouring.
D) Reinforced plastic.
E) Reinforced fiberglass.
F) Thermoplastic.
4) Depth. The minimum liquid depth of the
tank shall be 42 inches, and the maximum liquid depth shall be 72
inches.
5) Inlet and Outlet
Connections
A) The invert elevation of the
inlet shall be at least 2 inches above the liquid level in the tank.
B) The inlet and outlet openings of the
septic tank shall be provided with cast-in watertight openings.
6) Baffles. Septic tank baffles
shall meet the following requirements:
A)
Inlet baffles shall be provided and shall extend at least 6 inches below the
surface of the liquid.
B) Inlet
baffles shall be located no farther than 12 inches from the inlet
orifice.
C) Inlet and outlet
baffles shall have a clearance of at least one inch but not greater than 3
inches of free space between the underside of the tank lid and the
baffles.
D) Outlet baffles shall be
provided and shall extend to a depth of 40% of the liquid depth.
E) Outlet baffles shall be located no farther
than 6 inches from the outlet end wall.
F) Slip-in baffles shall extend the full
width of the tank.
G) The sides of
"V" or semi-circular type baffles shall fit tightly against the end wall of the
tank.
H) Venting shall be provided
through all baffles and a free vent area equal to the cross-sectional area of
the building shall be provided.
I)
Submerged pipe T-branches or sanitary tees may be used at the inlets and
outlets in lieu of baffles, provided that all of the above-stated distances and
depths are maintained.
J) Submerged
pipe T-branches or sanitary tees used as inlet baffles shall be 6 inches in
diameter or larger. Outlet baffles shall be 4 inches in diameter.
K) Submerged pipe T-branches or sanitary tees
shall meet the requirements of ASTM 2661, ASTM 2665 or ASTM 3034, or ASTM 2751,
provided that the pipe does not have an SDR (Standard Dimension Ratio) number
greater than 35.
L) When submerged
pipe T-branches or sanitary tees are used as baffles, it shall be the
responsibility of the septic tank manufacturer to assure proper location of
components during initial installation.
M) When a single compartment septic tank is
manufactured or used, a gas deflection baffle shall be provided below the
outlet baffle of the tank configured to deflect rising gas bubbles away from
the outlet structure and toward the interior of the tank. This baffle shall be
constructed of a durable material not subject to corrosion or decay. (Appendix
A, Illustration E, Exhibit C is an illustration.) An NSF International/ANSI
Standard 46, Section 10 septic tank filter may be used in lieu of the gas
deflector baffle. The septic tank filter baffle shall be installed so that it
is extended or suspended to a depth equal to 40% of the liquid level of the
tank. The tank access over the filter shall be provided with an access riser
that extends to 3 inches above the ground surface or greater.
7) Access. Access shall be
provided over the inlet and outlet of the tank to facilitate inspection and
cleaning. The manhole or access opening shall have a fitted lid with a minimum
dimension of 12 inches (width or diameter). Risers shall be watertight and
constructed of a durable material. If the top of the tank is greater than 12
inches below the ground surface, a riser with a minimum dimension of 12 inches
(width or diameter) shall be provided to bring access over the inlet and outlet
to within 12 inches of the ground surface. The joint between the septic tank
and the risers shall be watertight. If a 2-compartment tank is used, and the
tank has an opening over the wall between the compartments, the center opening
shall have access provided within 12 inches of the ground surface.
c) Capacity
1) Septic tanks for individual residences
shall be sized in accordance with Appendix A, Illustration F. Septic tanks for
any establishment other than residential property shall be sized in accordance
with the estimated flow provided in Appendix A, Illustration A and as provided
in subsection (c)(2).
2) The volume
below the liquid level for flows up to 500 gallons per day shall be at least
750 gallons. For flows greater than 500 gallons per day, the volume shall be
equal to at least 11/2 the estimated daily sewage flow. When the total flow
exceeds 1,350 gallons per day, 2 or more tanks in series, or a
multi-compartment tank, shall be installed.
d) Multiple Tanks or Compartments. When
multiple compartment septic tanks or multiple septic tanks in series are used,
the capacity of the first compartment or tank shall be 1/2 to 2/3 of the total
required capacity. Two-compartment tanks shall also comply with the following:
1) The wall separating the first and second
compartments shall be tight-fitting and designed to handle the differential in
pressure if one side is pumped.
2)
The wall separating the compartments shall extend to within 3 inches of the
tank lid and shall have a free vent area equal to the cross-sectional area of
the house sewer.
3) The center of
the opening between compartments shall be in line with the center of the inlet
and outlet openings.
4) The depth
to the invert of the opening between compartments shall be 40% of the liquid
depth.
5) A gas deflection baffle
shall be provided below the outlet baffle of the tank configured to deflect
rising gas bubbles away from the outlet structure and toward the interior of
the tank. This baffle shall be constructed of a durable material that is not
subject to corrosion or decay. An NSF International/ANSI Standard 46, Section
10 septic tank filter may be used in lieu of the gas deflector baffle. The
septic tank filter baffle shall be installed so that it is extended or
suspended to a depth equal to 40% of the liquid level of the tank. The tank
access over the filter shall be provided with an access riser that extends to 3
inches or more above the ground surface.
6) For a 2-compartment tank, openings with a
minimum dimension of 18 inches shall be located over the inlet and outlet of
the tank or 12-inch openings as follows:
A)
One located over the inlet;
B) One
over the outlet; and
C) One
centered over the compartment wall.
e) Septic Tank Installation
1) The septic tank shall be set level and
backfilled to prevent floatation or drifting of the tank. Level shall mean plus
or minus 1/2 inch in any direction (length or width or diameter of the
tank).
2) If the inlet, outlet or
access openings are to be set at or below the seasonal high water table, all
openings in the tank shall be made watertight using mastic, tar, silicone
caulk, etc.
3) There shall be no
connections, such as joints, splices or fittings, within the area of overdig
around the septic tank.
f) Abandoned Treatment Units. Septic tanks,
cesspools, pit privies, aerobic treatment plants and seepage pits that are no
longer in use shall be completely pumped. The floor and walls shall be cracked
or crumbled so that the tank will not hold water, and the tank shall be filled
with sand or soil. If the tank is removed from the ground, the excavation shall
be filled with soil.