Sanitation of Buildings

In other sections of the United States, however, the main drain trap and fresh air inlet are not permitted. In such places the house-drain runs directly to the sewer, cesspool, or septic tanks, without the intervention of a main or intercepting trap.

The gradients of the drains are usually arranged as to not only ensure the system being self-cleansing, but also so that they do not discharge their contents at such a rate that the solids are left behind to putrify on the sides of the channels. It is usual to fix the velocity at about 3 feet per second for these purposes.

Advantage may be taken of an inspection chamber or shaft to provide ventilation to the drains. All connections between branches and the main drain are made by specially designed pipes provided with junctions.

Drain Tests.—Drain testing is undertaken for two reasons : (a) to ensure that the system of a new house is satisfactory before the dwelling is inhabited, (b) to locate defects in systems already in use. The testing in each case differs somewhat as it is considered that new drains should be able to pass severer tests than those which have been in use some years. New drains are, therefore, usually subjected to the "water test" in which any length of the drain is first closed at the lower end by some form of plug or stopper, and the drain is then filled with water so as to give a maximum head of pressure of not more than about 6 feet. The stopper is fitted with an expanding rubber ring, and constructed in some cases so that the air can escape, and the required head may be obtained by adding vertical lengths of 1 inch diameter pipe to a similar plug at the upper end of the pipe line. A slight diminu tion in the head may be observed at the commencement of the test, due to absorption by the joints and possibly by the pipes, but this will soon cease, and no further drop should occur for a period of an hour. The pipe trenches should all be left open until the tests have been made, the inspector being thus able to locate any fault if indicated by a fall in water level. For drains already in use it is customary to use the "smoke test." For this machines are used which generate smoke and then, by means of fans or pistons, pump it into the branch or main drain. Compressed air tests are

also used, any leakage being shown on the gauge attached to the pump. Smoke "rockets" have been advocated in the past, but the amount of smoke generated is small and the effect is local. Smell tests, using peppermint, calcium carbide, etc., have also been used, but the difficulty in locating the leakage of a smell, and the great difficulty in preventing the chemical getting on the hands or clothes, has made this test almost obsolete. If smoke is used it is generated in a receiver connected to the fan or pump on one side and to a hose on the other, and is formed by the burning of oily waste, or any substance which will give off a dense cloud.

Obstructions in drains are usually removed by rods which can be jointed together to form any length, and occasionally fitted with brushes or scrapers.

Traps.

In British plumbing practice all parts of the drain age system, when there is any possibility of drain air entering the house, are disconnected by traps, the only exception being the soil pipe, which is connected to the drain by a bend. Such traps are placed either on the drainage system itself, or under each of the house plumbing fix tures and the "Seal" should al ways be about 2 in. to avoid the effect of evaporation. Gulley-traps are installed to disconnect roof-leaders and sink waste-pipes from the drainage system. For sink wastes the liquid has to pass along an open channel outside the building for a length of at least 18 in. before entering the trap. It is intended to so prevent grease entering the drain by causing it to cool and solidify and remain either in the channel or the trap.

Grease traps are frequently specially provided where large quantities of grease may be expected, as from the cooking de partments of hotels and clubs. The hot liquid enters near the base of the apparatus and leaves at the same level, and the grease rises to the surface where it cools and solidifies. The water area is made as large as practicable and a wire basket or galvanized iron i tray is provided to remove the grease, which operation should be frequently carried out.