A distribution box shall be installed between
a septic tank and a leaching facility to provide equal distribution.
Where the distribution system is dosed or the
slope of the inlet pipe is greater than 0.08, the distribution box
shall be provided with an inlet tee cutoff one inch above the outlet
invert.
The invert elevation of all outlets shall be
the same and shall be at least two inches below the inlet. Outlet
pipes shall be level for at least two feet.
The distribution box shall be provided with
a sump extending six inches below the bottom of the outlet pipe.
Distribution boxes shall be constructed of concrete
or other durable material. They shall be watertight and designed to
accommodate the necessary distribution laterals.
There shall be at least one four-inch outlet
for every pair of four-inch distribution laterals and at least one
six-inch outlet for every two pairs of four-inch distribution laterals.
Distribution boxes shall be installed on a level,
stable base that will not settle.
The distribution box shall be constructed in
such a manner as to provide ventilation of the disposal field, either
through a special vent or back through the building sewer.
Distribution boxes shall be provided with readily
removable covers of durable material. Systems designed for over 20,000
gallons per day shall have a minimum eighteen-inch manhole over each
distribution box, with metal frame and cover to finished grade.
