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

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Select lateral length.
IS used in this example.
A central manifold (Figure 7-24) design
Lateral length = y - 0.5 ft (for manifold)
= 32 ft
Select hole diameter and hole spacing for laterals. For this
example, l/4-in. diameter holes spaced every 30 in. are used,
although other combinations could be used.
Select lateral diameter. For l/4-in. hole diameter, 30-in.
hole spacing, and 32-ft lateral length, Figure 7-28 indicates
that either a l-l/4-in. or l-l/2-in. diameter lateral could be
used. The l-l/4-in. diameter is selected for this example.
Calculate lateral discharge rate. A 2-ft head is to be
malntalned 1r-1 the lateral.
For l/4-in. hole at 2 ft of head, Table 7-13 shows the hole
discharge rate to be 1.04 gpm.
Number of holes per lateral =
32-ft lateral length
2 . S-ft hole spacing
= 13
Lateral discharge rate = (13 holes/lateral) x (1.04 gpm/hole)
= 13.5 gpm/lateral
Select manifold size. There are to be four laterals (two on
either side of the center manifold) spaced 3 ft apart. A
manifold length of less than 5 ft is required (see Figure 7-
32).
For four laterals, 13.5 gpm/lateral, and manifold length less
than 5 ft, Figure 7-29 indicates that a l-l/2-in. diameter
manifold is required.
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