Figure 4-5. Deep pit latrine.
b. Latrine Pit. The pit is dug two feet wide and three and one-half feet long.
This will give the latrine box three inches of support on all sides. The depth of the pit
will depend on the estimated length of time the latrine is to be used. As a rough guide,
allow a depth of one foot for each week of estimated use plus one foot of depth for the
dirt cover. Generally, it is not desirable to dig the pit more than six feet deep because of
danger that the walls may cave in. Rock or high ground water levels often limit the
depth of the pit. In some types of soil, a support of planking or other material for the
sides may be necessary to prevent the wall from caving in. Earth should be packed
tightly around the bottom edges of the box in order to seal any openings through which
flies might gain entrance.
c. Vent. It is sometimes desirable to install a vent stack to release the moisture-
laden gases of decomposition. This prevents condensate from forming under the lids.
(The condensation could come in contact with an individual's back.) The vent stack
should extend from the upper part of the pit to about six feet above the ground. The
outside opening of the vent stack must be screened with wire (18-mesh or smaller) to
prevent flies and other insects from gaining entrance to the pit.
d. Maintaining the Latrine. In order to prevent flies breeding in the pit and to
reduce odors, it is necessary to keep the latrine box clean, the seat lids closed, and the
cracks sealed. A good fly control program must also be maintained in the area. The
box and the seats of the latrine should be scrubbed daily with soap and water. When
required, the latrine should be closed in the manner described in paragraph 4-9.