On-Site Wastewater Treatment and Disposal Systems - Forced ...

In summary, the final network design consists of four 32-ft laterals l-
l/4 in. in diameter (two on each side of a 3-in. diameter center mani-
fold. The inverts of the laterals are perforated with l/4-in. holes
spaced every 30 in.
90 Other Distribution Networks
Several other distribution network designs are occasionally used, Among
these are the inverted network and leaching chambers. While users of
these networks claim they are superior to conventional networks, compre-
hensive evaluations of their performance have not been made.
Inverted Network: This network uses perforated pipe with the holes lo-
cated in the crown rather than near the invert (32). This arrangement
is designed to provide more uniform distribution of wastewater over a
large area, and to prolong the life of the field by collecting any set-
tleable solids passing out of the septic tank in the bottom of the pipe.
Water-tight sumps are located at both ends of each inverted line to fa-
cilitate periodic removal of the accumulated solids.
Leaching Chambers: In place of perforated pipe and gravel for distri-
bution and storage of the wastewater, this method employs open bottom
chambers. The chambers interlock to form an underground cavern over the
soils' infiltrative surface. The wastewater is discharged into the cav-
ern through a central weir, trough, or splash plate and allowed to flow
over the infiltrative surface in any direction. Access holes in the
roof of the chamber allow visual inspection of the soil surface and
maintenance as necessary. A large number of these systems have been in-
stalled in the northeastern United States (see Figure 7-33).
7.2.8.2 Materials
Three to 4-in. (8- to lo-cm) diameter pipe or tile is typically used for
nonpressurized networks. Either perforated pipe or 1-ft (30 cm) lengths
of suitable drain tile may be used. The perforated pipe commonly has
one or more rows of 3/8- to 3/4-in. (l.O- to 2.0-cm) diameter holes.
Hole spacing is, ,not critical. Table 7-15 can be used as a guide for
acceptable materials for nonpressurized networks.
Plastic pipe is used for pressure distribution networks because of the
ease of drilling and assembly. Either PVC Schedule 40 (ASTM D 2665) or
ABS (ASTM 2661) pipe may be used.
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