placed in the absorption trench. Figure 10-6 shows
a typical layout of a leaching field.
The type of soil at the location of the field will
dictate the width of the trench. Sand and sandy
loam require a width of 1 foot, loam and sand and
clay mixture 2 feet, clay with some gravel 3 feet.
Note these are minimum trench widths based on the
type of soil encountered at the jobsite.
Placing the leaching pipe below the frost line
to prevent freezing is not necessary. Under no
circumstances can you lay leach pipe below the
ground water level. When digging the absorption
trenches, you must consider the lengths of each
lateral and their spacing in relation to each other.
Do not make any lateral longer than 100 feet
in length. Table 10-17 shows the size and
spacing requirements for disposal fields.
After the trenches are laid out and dug,
filler material must be placed along with the
actual pipe. The filler material may be washed
gravel, crushed stone, slag, or clean bank-run
gravel ranging in size from 1/2 to 2 1/2
inches. Filler material in the trench should not
be less than 6 inches deep below the bottom
of the pipe. It should be at least 2 inches
above the pipe. To prevent backfill soil from
filling the voids in the filler material, it is
recommended that a 3-inch
Figure 10-6.Typical layout of a subsurface tile system.