Sewage.—Few subjects relating to health are of greater importance than the proper disposal of the refuse and waste matter of the household. Even if free from the specific germs of disease, the organic matters contained in sewage give rise to noxious emanations, which, when inhaled, lower the tone of the system and render it an easy prey to disease.
Dangers of the Soil Pipe.—It is chiefly through the soil pipe that cess-pool and sewer gas finds its way into the house. The return of these foul emanations is often caused by the force of their own expansion and sometimes by the pressure of the sewer air behind them. The water-traps afford but a slight barrier to their progress. Every drain pipe leading to cess-pool or sewer should be connected with a ventilating shaft which will carry the foul vapors above the roof of the house, and as far away from the windows as possible.
The Medical Officer for Edinburgh, in a recent report, declared that wherever water-closets had been introduced, in the course of one year there were double the number of deaths from typhoid and scarlet-fever, and that any epidemic fever occurring in these houses assumed a character of malignant mortality.
Disinfectants.—Chemical disinfectants are used by many good housewives, and are helpful, but they cannot be wholly relied upon. Cleanliness, ventilation, and dryness are the natural disinfectants. Artificial disinfectants can no more be substituted for them than perfumes can be made to take the place of soap and water.
Sewer Gas.—This poisonous gas is known chiefly by its effect. It frequently passes the water-traps and enters our sleeping and living rooms, there to do its fatal work. The alternate floods of hot and cold water open the joints of iron pipes, and allow the gas to escape. Leaden gas pipes decay and become perforated, with the same result. Dr. Fergus, in his pamphlet “The Sewage Question,” says: “For some years I have insisted on a careful examination of the soil pipes wherever I have cases of typhoid or diphtheria, and in every case where I could get this carefully carried out I have detected perforated pipes, or have found sewer air getting into the houses in some other way. In many cases the plumbers have declared pipes to be all right, which turned out to be very defective when uncovered.”
Water-Traps.—These are not so effective in preventing the escape of sewer gas as they are considered to be. Experiments with glass tubes shaped and arranged just as the ordinary water-traps in sinks and closets are arranged have shown that the light gases pass through by the top of the bend, and the heavy gases by the bottom. A rush of wind up the mouth of a sewer, or a heavy dash of rain which fills the sewer and reduces the air space, so increases the pressure of the gas within the sewer and soil pipe that the ordinary water-traps are not able to resist it.
Water-traps that are not used for a time become death-traps. The water soon evaporates, and affords an unobstructed channel for the conveyance of foul gases from cess-pool or sewer to the rooms of the house. Houses that are vacated for the summer, and that are without tenants for a time, should be thoroughly cleaned and ventilated, and have all pipes and drains flushed with water before being occupied.
Size, Flow, and Fall of Drain Pipes.—The efficiency of a drain or sewer depends upon its capacity, its slope or incline, and the velocity of its flow. If the amount of water flowing is proportionate to the size of the conduit, sewers of different sizes give the same velocity at different inclinations. A ten-foot sewer with a fall of two feet per mile, a five-foot sewer with a fall of four feet per mile, a two-foot sewer with a fall of ten feet per mile, and a one-foot sewer with a fall of twenty feet per mile will have the same velocity provided they are filled in proportion to their capacity. The ten-foot sewer will require one hundred times as much sewage as will the one-foot sewer. If it has less, the velocity of its stream will be correspondingly diminished. It is especially important, therefore, that the size of the conduit be adapted to the volume of the stream, as well as to the slope or inclination.
An experienced engineer gives a velocity of three feet per second as the least that should be allowed for the outlet drain of a house. To secure this flow a four-inch drain should have a minimum inclination of one inch in ninety-two; a six-inch drain, one in one hundred and thirty-seven; a nine-inch drain, one in two hundred and six; and to attain the above velocity of three feet per second at these inclinations they must run not less than half full. The great purpose of all modern sewage systems is to carry off all waste matters before they have time to decompose.
Joints of Drain Pipes.—These should be made so smooth within as not to impede the flow of sewage, nor become obstructed by catching thread, strings, hair, and other floating substances. They should be so tight as absolutely to prevent any leakage of either fluid or gaseous matter, and render impossible the entrance of the small filaments of the roots of trees growing along their course. They should be supported on solid pillars of brick or stone, and not spiked to cellar walls where a slight settling will force the joints and cause a leak. They should be so firmly supported at every point that after the joints have been cemented no possible change of direction or slope of pipe can occur. Any such change is sure to work disaster.