Current through Register Vol. 39, No. 6, September 16, 2024
(a) A septic tank or dosing tank shall be
watertight, structurally sound, and not subject to excessive corrosion or
decay. Septic tanks shall be of two-compartment design. The inlet compartment
of a two-compartment tank shall hold between two-thirds and three-fourths of
the total tank capacity. Septic tanks shall have an approved effluent filter
and access devices. The effluent filter shall function without a bypass of
unfiltered wastewater, sludge or scum. The effluent filter case shall be
designed to function as a sanitary tee with the inlet extending down to between
25 and 40 percent of the liquid depth. The requirement(s) for an effluent
filter and access devices shall apply to septic tanks for which a Construction
Authorization is issued on or after January 1, 1999. A properly designed dosing
siphon or pump shall be used for discharging sewage effluent into nitrification
lines when the total length of such lines exceeds 750 linear feet in a single
system and as required for any pressure-dosed system. When the design daily
flow from a single system exceeds 3,000 gallons per day or when the total
length of nitrification lines exceeds 2,000 linear feet in a single system,
alternating siphons or pumps shall be used which shall discharge to separate
nitrification fields. The dose volume from pump or siphon systems shall be of
such design so as to fill the nitrification lines from 66 percent to 75 percent
of their capacity at each discharge except as required for low-pressure
distribution systems. The discharge rate from dosing systems shall be designed
to maximize the distribution of the effluent throughout the nitrification
field. Septic tanks installed where the top will be deeper than six inches
below the finished grade shall have an access manhole over each compartment
with cover, extending to within six inches of the finished grade, having a
minimum opening adequate to accommodate the installation or removal of the
septic tank lid, septage removal, and maintenance of the effluent filter. When
the top of the septic tank or access manhole is below the finished grade, the
location of each manhole shall be visibly marked at finished grade. Any system
serving a design unit with a design sewage flow greater than 3,000 gallons per
day shall have access manholes that extend at least to finished grade and be
designed and maintained to prevent surface water inflow. The manholes shall be
sized to allow proper inspection and maintenance. All dosing tanks shall have a
properly functioning high-water alarm. The alarm shall be audible and visible
by system users and weatherproof if installed outdoors. The alarm circuit shall
be provided with a manual disconnect in a watertight, corrosion-resistant
outside enclosure (NEMA 4X or equivalent) adjacent to the dosing
tank.
(b) Minimum liquid capacities
for septic tanks shall be in accordance with the following:
(1) Residential Septic Tanks (for each
individual residence or dwelling unit):
|
Number of Bedrooms |
Minimum Liquid Capacity |
Equivalent Capacity Per Bedroom |
|
3 or less |
900 gallons |
300 gallons |
|
4 |
1,000 gallons |
250 gallons |
|
5 |
1,250 gallons |
250 gallons |
(2) Septic tanks for large residences,
multiple dwelling units, or places of business or public assembly shall be in
accordance with the following:
(A) The liquid
capacity of septic tanks for places of business or places of public assembly
with a design sewage flow of 600 gallons per day or less shall be determined in
accordance with the following: V = 2Q; where V is the liquid capacity of the
septic tank and Q is the design daily sewage flow. However, the minimum
capacity of any septic tanks shall be 750 gallons.
(B) Individual residences with more than five
bedrooms, multiple-family residences, individual septic tank systems serving
two or more residences, or any place of business or public assembly where the
design sewage flow is greater than 600 gallons per day, but less than 1,500
gallons per day, the liquid capacity of the septic tank shall be designed in
accordance with the following: V = 1.17Q + 500; where V is the liquid capacity
of the septic tank and Q is the design daily sewage flow. The minimum liquid
capacity of a septic tank serving two or more residences shall be 1,500
gallons.
(C) Where the design
sewage flow is between 1,500 gallons per day and 4,500 gallons per day, the
liquid capacity of the septic tank shall be designed in accordance with the
following: V = 0.75Q + 1,125; where V is the liquid capacity of the septic tank
and Q is the design daily sewage flow.
(D) Where the design sewage flow exceeds
4,500 gallons per day, the septic tank shall be designed in accordance with the
following: V = Q; where V is the liquid capacity of the septic tank and Q is
the design daily sewage flow.
(E)
The minimum liquid capacity requirements of Subparagraph (b)(2) of this Rule
shall be met by use of a single two-compartment septic tank or by two tanks
installed in series, provided the first tank is constructed without a baffle
wall and contains at least two-thirds of the total required liquid
capacity.
(c)
The following are minimum standards of design and construction of pump tanks
and pump dosing systems:
(1) The liquid
capacity of a pump tank shall be considered as the entire internal volume with
no additional requirement for freeboard. Pump tanks shall have a minimum liquid
capacity in accordance with the following:
(A)
Pump tanks for systems with nitrification fields installed in Soil Group I, II,
or III soils, as defined in these Rules, shall have a minimum liquid capacity
equal to two-thirds of the required septic tank liquid capacity.
(B) Pump tanks for systems installed in Group
IV soils shall have a minimum liquid capacity equal to the required septic tank
liquid capacity.
(C) The minimum
liquid capacity of any pump tank shall be 750 gallons.
(D) An alternate method to determine minimum
liquid capacity of a pump tank shall be to provide for the minimum pump
submergence requirement (Subparagraph (c)(5) of this Rule), the minimum dose
volume requirement (Paragraph (a) of this Rule), and the minimum emergency
storage capacity requirement. The emergency storage capacity requirement is
determined based on the type of facility served, the classification of surface
waters which would be impacted by a pump tank failure, and the availability of
standby power devices and emergency maintenance personnel. The emergency
storage capacity shall be the freeboard space in the pump tank above the
high-water alarm activation level plus the available freeboard space in
previous tankage and in the collection system below the lowest ground elevation
between the pump tank and the lowest connected building drain invert. The
minimum emergency storage capacity for residential systems and other systems in
full-time use on sites draining into WS-I, WS-II, WS-III, SA, SB, and B waters
shall be 24 hours, without standby power, or 12 hours with standby power
manually activated, or four hours with standby power automatically activated or
with a high-water alarm automatically contacting a 24-hour maintenance service.
The minimum emergency storage capacity for systems not in full-time use and for
all systems at sites draining into all other surface waters shall be 12 hours
without standby power, or eight hours with standby power manually activated, or
four hours with standby power automatically activated or with a high-water
alarm automatically contacting a 24-hour maintenance service.
(E) Notwithstanding Paragraphs (c)(1)(A)-(D),
other criteria for pump tank capacity may be approved by the local health
department and the State for raw sewage lift stations, pressure sewer systems,
and systems with design flows exceeding 3,000 gallons per day.
(2) The effluent pump shall be
capable of handling at least one-half inch solids and designed to meet the
discharge rate and total dynamic head requirements of the effluent distribution
system. The pump shall be listed by Underwriter's Laboratory or an equivalent
third party electrical testing and listing agency, unless the proposed pump
model is specified by a registered professional engineer.
(3) Pump discharge piping shall be of
Schedule 40 PVC or stronger material and adequately secured. Fittings and
valves shall be of compatible corrosion-resistant material. A threaded union,
flange, or similar disconnect device shall be provided in each pump discharge
line. All submersible pumps shall be provided with a corrosion-resistant rope
or chain attached to each pump enabling pump removal from the ground surface
without requiring dewatering or entrance into the tank. Valves shall also be
readily accessible from the ground surface.
(4) Antisiphon holes (three-sixteenth inch)
shall be provided when the discharge or invert elevation of the distribution
system is below the high-water alarm elevation in the pump tank, or in
accordance with pump manufacturer's specifications. Check valves shall be
provided when the volume of the supply line is greater than 25 percent of the
dosing volume, or in accordance with pump manufacturer's specifications. When
provided, the antisiphon hole shall be located between the pump and the check
valve.
(5) Sealed mercury control
floats or similar devices designed for detecting liquid levels in septic tank
effluent shall be provided to control pump cycles. A separate level sensing
device shall be provided to activate the high-water alarm. Pump-off level shall
be set to keep the pump submerged at all times or in accordance with the
manufacturer's specifications. A minimum of 12 inches of effluent shall be
maintained in the bottom of the pump tank. The high-water alarm float shall be
set to activate within six inches of the pump-on level. The lag pump float
switch, where provided, shall be located at or above the high-water alarm
activation level.
(6) Pump and
control circuits shall be provided with manual circuit disconnects within a
watertight, corrosion-resistant, outside enclosure (NEMA 4X or equivalent)
adjacent to the pump tank, securely mounted at least 12 inches above the
finished grade. The pump(s) shall be manually operable without requiring the
use of special tools or entrance into the tank for testing purposes. Conductors
shall be conveyed to the disconnect enclosure through waterproof, gasproof, and
corrosion-resistant conduits, with no splices or junction boxes provided inside
the tank. Wire grips, duct seal, or other suitable material shall be used to
seal around wire and wire conduit openings inside the pump tank and disconnect
enclosure.
(7) For systems
requiring duplex and multiplex pumps, a control panel shall be provided which
shall include short-circuit protection for each pump and for the control
system, independent disconnects, automatic pump sequencer, hand-off-automatic
(H-O-A) switches, run lights, and elapsed time counters for each pump. Alarm
circuits shall be supplied ahead of any pump overload or short circuit
protective devices. The control panel must be in a watertight,
corrosion-resistant enclosure (NEMA 4X or equivalent) unless installed within a
weathertight building. The panel shall be protected from intense solar
heating.
(8) Dual and multiple
fields shall be independently dosed by separate pumps which shall automatically
alternate. The supply lines shall be "H" connected to permit manual alternation
between fields dosed by each pump. "H" connection valving shall be readily
accessible from the ground surface, either from the pump tank access manhole or
in a separate valve chamber outside the pump tank. Other equivalent methods of
dosing dual or multiple fields may be approved by the State.
(9) The pump tank shall have a properly
functioning high-water alarm. The alarm circuit shall be supplied ahead of any
pump overload and short circuit protective devices. The alarm shall be audible
and visible by system users and weatherproof if installed outdoors in an
enclosure (NEMA 4X or equivalent).
(d) Siphons and siphon dosing tanks may be
used when at least two feet of elevation drop can be maintained between the
siphon outlet invert and the inlet invert in the nitrification field
distribution system.
(1) Siphon dosing tanks
shall be designed in accordance with the minimum dose requirements in this Rule
and shall meet the construction requirements of this Section. The siphon dose
tank shall provide at least 12 inches of freeboard, and the inlet pipe shall be
at least three inches above the siphon trip level. The high-water alarm shall
be set to activate within two inches of the siphon trip level.
(2) Siphon dosing tanks shall have a
watertight access opening over each siphon with a minimum diameter of 24 inches
and extending to finished grade and designed to prevent surface water
inflow.
(3) The slope and size of
the siphon discharge line shall be sufficient to handle the peak siphon
discharge by gravity flow without the discharge line flowing full. Vents for
the discharge lines shall be located outside of the dosing tank or otherwise
designed to not serve as an overflow for the tank.
(4) All siphon parts shall be installed in
accordance with the manufacturer's specifications. All materials must be
corrosion-resistant, of cast iron, high density plastic, fiberglass, stainless
steel, or equal.
(5) Siphon dosing
tanks shall have a properly functioning high-water alarm that is audible and
visible by system users and weatherproof if installed outdoors in an enclosure
(NEMA 4X or equivalent).
(e) Raw sewage lift stations shall meet the
construction standards of this Section and all horizontal setback requirements
for sewage treatment and disposal systems in accordance with Rule .1950(a) of
this Section unless the station is a sealed, watertight chamber, in which case
the setback requirements for collection sewers in Rule .1950(e) of this Section
shall apply. Sealed, watertight chambers shall be of a single, prefabricated
unit, such as fiberglass, with sealed top cover, and preformed inlet and outlet
pipe openings connected with solvent welds, O-ring seals, rubber boots,
stainless steel straps, or equivalent. Dual pumps shall be provided for
stations serving two or more buildings or for a facility with more than six
water closets. Pumps shall be listed by Underwriter's Laboratories or an
equivalent third party electrical testing and listing agency, and shall be
grinder pumps or solids-handling pumps capable of handling at least three-inch
spheres unless the station serves no more than a single water closet, lavatory,
and shower, in which case two-inch solids handling pumps shall be acceptable.
Minimum pump capacity shall be 2.5 times the average daily flow rate. The
dosing volume shall be set so that the pump-off time does not exceed 30
minutes, except for stations serving single buildings, and pump run-time shall
be from three to ten minutes at average flow. Pump station emergency storage
capacity and total liquid capacity shall be determined in accordance with
Paragraph (c)(1)(D) of this Rule except for a sealed, watertight chamber
serving an individual building, in which case a minimum storage capacity of
eight hours shall be required. All other applicable requirements for pump tanks
and pump dosing systems in accordance with Paragraph (c) of this Rule shall
also apply to raw sewage lift stations.
