layer of medium-screened gravel with another
layer of fine-screened gravel, untreated paper, or
straw of 2 to 3 inches in depth in the trench.
Pipe should be laid with a minimum pitch
of 2 inches to a maximum pitch of 4 inches per
100 feet, When open joints are used, they must
not be spaced more than 1/2 inch apart.
Asphalt-treated paper should be used to cover
the joint. The open joint allows for free
discharge of solids from the line to the trench.
The asphalt-treated paper prevents gravel from
entering the pipe.
The layout of the field requires attention to
detail to prevent future maintenance and
operation troubles. When the field is laid on
sloping ground, the flow must be distributed so
each lateral gets a fair portion of the flow.
Individual lines should be kid nearly parallel to
land contours, Leaching fields are commonly laid
out either in a herringbone pattern (fig. 10-6) or
with the laterals at right angles to the main
distribution pipe. Little or no maintenance is
required for leaching fields. Preventive
measures, such as excluding all vehicle traffic
and not planting trees or shrubs in the field area,
should ensure trouble-free operation for many
years. When a leaching field becomes
inoperable, you must replace it with a new
system. Tree or shrub roots are a major factor
in leaching-field failure. This requires the
replacement of field components and complete
Table 10-17.Size and Spacing for Disposal Fields