from 1 foot at the central pit to 1-1/2 feet at the outer ends. The pit and trenches are
filled with material similar to that used in the soakage pit. Two such units should be built
for every 200 persons fed, each unit to be used on alternate days. A grease trap should
also be used with a soakage trench. A soakage trench is closed in the same way as a
Figure 6-14. Soakage trench with barrel filter grease trap in place.
6-18. GREASE TRAPS
The grease trap should be of sufficient capacity so that the hot, greasy water
being added will not heat the cool water already present in the trap. Otherwise, the
grease will remain uncongealed and will pass through the trap. A grease trap is
provided for each soakage pit except those under showers.
a. Baffle Grease Trap. A baffle grease trap may be made from half of a barrel
which has been cut in two or from a box which has been divided vertically into unequal
chambers by a wooden baffle (figure 6-15). This baffle should extend to within one inch
of the bottom. The wastes are poured through a strainer into the larger chamber (about
two-thirds of the capacity of the box or barrel); they then pass under the baffle and flow
out of the smaller chamber. In the larger chamber, the trap should have a removable lid
and a removable strainer. The strainer, which may be a box with openings in the
bottom, is filled with straw or burlap to remove coarser solids; it must be cleaned
frequently to prevent clogging. A one-inch pipe, inserted 3 to 6 inches below the top of
the smaller chamber, acts as an outlet and carries the liquid from the trap to the
soakage pit. To ensure proper operation of the trap, it must be cleaned frequently.
Grease must be removed, the trap drained, and the sediment in the bottom removed.
The removable strainer may be cleaned by scrubbing it with soap and water. The
grease, sediment, and strainer material should be either burned or buried.