[CHAPTER XXV.]
HOUSE DRAINAGE.
The Removal of Impurities.—In order that health may be maintained in any inhabited house, it is essential that the impurities produced by animal life should be removed. These impurities may be divided into two classes—the first including the gaseous and volatile products evolved from the lungs and skin; and the second, the liquid excretion from the kidneys, and the solid from the bowels. The former are got rid of by efficient ventilation and by cleanliness; the latter, ought to be as quickly removed, but require more elaborate arrangements to ensure this.
The average daily amount of solid excreta is about 4 ounces, and of fluid excreta about 50 ounces for each adult male. Taking all ages and both sexes into consideration, the amount per head is about 2¾ ounces of fæces and 32 ounces of urine. When dried, the daily fæces amount to 1·04 oz., the daily urine to 1·74 oz., so that the manurial value as well as the possible polluting power of urine is much greater than that of the fæces.
After a variable interval urine and fæces begin to decompose, ammonia and fœtid gases being disengaged in large quantities. Urea the chief constituent of urine is decomposed into carbonic acid and carbonate of ammonia. Thus
CH₄N₂O + 2H₂O = (NH₄)₂CO₃
In addition to the excreta, house-slops have to be got rid of, and “dust.” House-slops vary greatly in quantity, but probably amount to as much as sixteen gallons per head daily. They consist chiefly of the water used in cooking and washing and for baths. It would be a mistake to suppose that only urine and fæces need careful disposal. There are masses of decaying epithelium from lavatories and baths, organic matters from soiled apparel, and various organic matters from culinary operations, all of which may cause serious nuisance unless promptly disposed of.
The Dust consists chiefly of the ashes from fires; but the dust-bin also forms a favourite refuge for kitchen refuse, composed of various animal and vegetable matters, as well as for broken pots and tins. It is dealt with apart from the house-slops and excreta, except in certain dry methods of disposal of sewage.
Two chief plans of getting rid of the sewage have been proposed, though there are many varieties of these. They are—
- 1. The Water Method, and
- 2. The Dry Methods.
For towns the water carriage of sewage is indispensable, and in this chapter we shall confine ourselves to the part of this system which relates to the Drainage of the House.