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< prev - next > Water and sanitation Sanitation KnO 100427_Ventilated improved pit latrines (Printable PDF)
Ventilated improved pit latrines
Practical Action
Mix enough concrete to fill the hole in the
proportions; 1 part cement; 2 parts sand; 4
parts gravel. Add just enough water to shovel
the concrete. With the squat and chimney
hole form in place, pour about one third of the
concrete into the smooth, shallow hole. Using
the pimbo, pound down a layer 2.5 to 3cm
thick. Use a clean nail to check the
thickness. Insert it, then remove it and
measure the cement marks.
A pimbo
Figure 9: The mesh is covered with more concrete
Then lay the cut wire mesh on top of the
concrete. Check to see that the hole forms are still in their proper places.
Adjust if necessary so that the weld mesh wires do not quite touch the forms.
Then pour a second layer of concrete 4.5 5cm thick, onto the reinforcement.
Trowel it flat. After it has set,
splash water on the concrete and
cover it with plastic sheeting.
Keep it damp and covered with
plastic for 7 days. After the
concrete has cured for 7 days, roll
the slab over to the latrine pit.
Mortar the bricks and lay the slab
on top.
Figure 10: Moving the slab
Lay down the first course of bricks very
carefully. Then mortar underneath and
between the bricks.
Alternate the vertical joints of courses of
Figure 11: Preparing for the slab
bricks and continue up to 2 meters (6.5 ft)
high. Mortar in place the flyscreen just below the foremost course of bricks on
the chimney. The chimney should be two bricks higher than the top of the roof.
Figure 12: A spiral wall
Figure 13: A square wall