The Privy Vault is the general mode of sewage disposal in villages, some towns, and even in some large cities, wherever sewers are not provided. In its primitive and unfortunately common form, the privy vault is nothing but a hole dug in the ground near or at some distance from the house; the hole is but a few feet deep, with a plank or rough seat over it, and an improvised shed over all. The privy is filled with the excreta; the liquids drain into the adjacent ground, which becomes saturated, and contaminates the nearest wells and water courses. The solid portion is left to accumulate until the hole is filled or the stench becomes unbearable, when the hole is either covered up and forgotten, or the excreta are removed and the hole used over again. This is the common privy as we so often find it near the cottages and mansions of our rural populace, and even in towns. A better and improved form of privy is that built in the ground, and made water-tight by being constructed of bricks set in cement, the privy being placed at a distance from the house, the shed over it ventilated, and the contents of the privy removed regularly and at stated intervals, before they become a nuisance. At its best, however, the privy vault is an abomination, as it can scarcely be so well constructed as not to contaminate the surrounding soil, or so often cleaned as to prevent decomposition and the escape of poisonous gases.

The Pail System is an economic, simple, and, on the whole, very efficient method of removing fresh excreta. The excreta are passed directly into stone or metal water- and gas-tight pails, which, after filling, are hermetically covered and removed to the places for final disposal. This system is in use in Rochedale, Manchester, Glasgow, and other places in England.

The pails may also be filled with dried earth, ashes, etc., which are mixed with the excreta and convert it into a substance fit for fertilization.

The Pneumatic System is a rather complicated mechanical method invented by Captain Lieurneur, and is used extensively in some places. In this system the excreta are passed to certain pipes and receptacles, and from there aspirated by means of air exhausts.

The Water-carriage System.—We now come to the modern mode of using water to carry and flush all sewage material. This method is being adopted throughout the civilized world. For it is claimed a reduction of the mortality rate issues wherever it is introduced. The water-carriage system presupposes the construction and existence of pipes from the house to and through the street to the place of final disposition. The pipes running from the house to the streets are called house sewers; and when in the streets, are called street sewers.

The Separate and Combined Systems.—Whenever the water-carriage system is used, it is either intended to carry only sewage proper, viz., solid and liquid excreta flushed by water, or fain water and other waste water from the household in addition. The water-carriage system is accordingly divided into two systems: the combined, by which all sewage and all waste and rain water are carried through the sewers, and the separate system, in which two groups of pipes are used—the sewers proper to carry sewage only, and the other pipes to dispose of rain water and other uncontaminated waste water. Each system has its advocates, its advantages and disadvantages. The advantages claimed for the separate system are as follows:

(1) Sewers may be of small diameter, not more than six inches.

(2) Constant, efficient flow and flushing of sewage.

(3) The sewage gained is richer in fertilizing matter.