For rural areas latrine should
be cheap but at the same time clean and hygienic. Villagers cannot afford to
construct septic tank which are costly. Water seal pit latrine known as
sanitary pit latrine is very cheap and suitable for villages. Sanitary pit
latrine are of two types, one in which the pit is directly under the latrine
and the other in which the pit is behind or outside the latrine. In both types
the latrine pan is provided with a trap for water seal to prevent the gas to
come out. Direct pit type is cheaper but has certain disadvantages as when the
pit gets full or the pit falls due to bad or soft soil, the whole latrine
together with its structure is to be shifted over a new pit. In the second type
the latrine structure and floor with pan and trap remain permanently at the
same place, the pit may be changed by a new one and connected with the latrine.
Fig.
The latrine structure should be
of brick wall with roof as it suits the pocket of the individual. The floor
should be rammed earth with brick flat laid in 1:5 cement mortar and finished
with 12 mm (1/2”) thick cement plaster 1:3. The floor is given 12 mm (1/2”)
slope towards pan from all sides to wash drain water into the pan.
The pit usually of 80 cm
(2’-9”) diameter and 2 to 3 meters (2 ½”) thick R.C.C. slab cover reinforced
with 6 mm (1/4”) diameter mild steel bars 20 to 25 cm (8” to 10”) spacings.
The cover may be given slight camber for strength. The cover may be of stone slab where available cheaply. The upper portion of the pit may be lined with two layers of brick in cement mortar for the seat of the slab and for protection from sides. Over the pit cover 15 cm (6”) earth cover should be given.
The latrine pan is of precast
cement mortar 1:3 cement and coarse sand finished smooth 48 cm (19”) long and
the water seal trap is of a separate precast cement mortar finished smooth. The
pan and trap are fitted in position before the floor is laid. The connecting
pipe is also of precast cement mortar 6.5 cm (2 1/2”) diameter and may be made
with curvature so that the pipe may be turned to connect the pan to the second
pit when required. The joint of trap with latrine pan should be made with 1:3
cement mortar. The joint of pipe with the trap should be made with cement
mortar with outer surface finished with 1:3 cement mortar so that pipe may be
taken out and turned over to connect with the second pit. The connecting pipe
should be laid with a slope of 1 in 10 for quick and easy flow of the sewage.
One pit may run for two to five years depending on the number of users and the nature of the soil. The pit works both as septic tank and soak-pit. The septic or anaerobic biological decomposition may not be complete if sufficient water is not used. The gas generated in the pit is absorbed in the soil. When one pit is filled up another pit may be dug by the side and connected with the latrine and cover is shifted to the new pit and is used again for a number of years. If the soil is sandy or soft the pit may be lined with brick either dry brick without mortar may be used or honey comb brick walling may be made with 1:10 cement mortar. If two lined pits are made these may be used alternately and the arrangement will be of a permanent nature. The cleaning of the pit should be done after ninety days of its last use and the material from the pit may be used as manure.
For flushing one or two mugs of
water is usually sufficient to flush the faces into the pit but it is better to
flush once daily with sudden pouring of a bucket of water.
The latrine may be located at one corner of the premises at as distance of about 6 meters (20’) from the living house and a distance of 15 meters (50’) from a source of water.
For direct pit type latrine the
pan and water seal tap are cast in one piece. Floor is of precast R.C.C. slab
with hole for fitting the pan, which also serves as cover of the pit.
