The methods suitable to any given home will depend whether or not domestic water pressure is available. In the absence of domestic water pressure either of the two following methods may be employed: (a) The So-called Chemical Closets.—These are simple in stallations for the interior of the dwelling, in which the excreta is received into a strong caustic solution, which disinfects the material. If properly cared for they will probably give satis factory results (Fig. 23).
(b) Privies.—A satisfactory privy should protect the excreta from flies, rats, hens, pigs, etc., and should be well ventilated to permit the ready evaporation of the liquid excreta. Their successful operation depends upon the degree of simplicity in their construction, as a general proposition those whose success ful operation requires continuous care are neglected sooner or later. All should be well screened and have a tight seat cover. Privies are usually of the following types: I. Vaulted.—The excreta are deposited into a pit or vault underneath. The pit should be made water tight by means of concrete walls and bottom (Fig. 24).
2. Pail or C an P rivies .—The excreta are deposited in large pails or buckets fitted underneath the seat. At voiding the person using the privy may cover the excreta with a thin layer of dry earth or ashes. They require constant attention, are apt to be neglected and hence, if privately controlled, are troublesome (Fig. 25). The wide spread employment of this type of privy in
unsewered towns, or unsewered areas of towns, should be under municipal supervision. Provision should be made for the ex change of receptacles at frequent, regular intervals, if satisfac tory results are to be secured. The expense of maintainence of such a system is high, which tends to stimulate a desire for the early installation of a sewerage system. The excreta (or night soil) are disposed of either by burial or incineration.
3. Leaching Privies.—These are apt to be unsatisfactory or dangerous. No pit is provided and the excreta are deposited on the surface of the ground. They should be located with care and water carriage is employed to transport the excreta to the point of disposal. These are of two main types: (a) Vaulted Cesspools.—These have concrete bottoms, sides and top, and are in reality septic tanks. The sludge should be burned, buried, or disinfected, while the effluent is best dis posed of by subsurface irrigation (Figs. 26, 27).
(b) Leaching Cesspools.—These do not have either a light bottom or walls. The liquid contents escape into the soil below the zone of active oxidation and hence may contaminate the ground water for some distance. They should not be used in clay or gravely soils or in limestone regions (Fig. 28).