DOUSE SEWERAGE or DRAINAGE includes every thing required to remove fouled water from the house to the sewer. The pipes from each sepa rate fixture are known as waste pipes; they run to one or more soil pipes, the soil pipe being the vertical run of pipe from the highest fixture to the cellar: the house drain extends from the foot of the soil pipe to a point near the cellar wall, and the house sewer from the latter point to the street sewer. Waste pipes, particularly short runs from washbowls and minor fixtures. may be of lead. but, generally speaking, cast or wrought iron is preferable for important wastes. All soil pipes and the house drain should also lie of cast iron. Heavy pipe should be used throughout. The house sewer should be of extra heavy iron through and a short distance beyond the founda tion. after which vitrified clay is permissible. All soil and waste pipes should be carried up through the roof. Traps are placed below each fixture and a main trap is generally set just in side the cellar wall. All main traps should have fresh air inlets or a pipe extending from the inner end of the trap to the outer air. This pro-' rides for a circulation of air through the house drain and soil pipe. An increasing number of sanitary engineers favor the omission of the main trap, thus insuring a thorough ventilation of the house and street sewerage system through the numerous soil pipes at one extremity and the street manholes at the other. The object of a
trap is to prevent foul air from the house or street sewerage system from entering the house. To this end the simplest and most prac tice is to form a water seal by making a bend in the pipe shaped like the letter LT or like the letter 5, the former being called a U-trap and the latter an Strap. Bell traps are formed by inverting a hell or cup over the upper and open end of a pipe, the whole being so adjusted that the edge of the pipe is always submerged. Grease traps may he described as enlargements on waste pipes to retain grease instead of allowing it to pass on and clog the sewers. They are most commonly used on the waste or drain pipes of large kitchens. Vent pipes were formerly run from the back of each trap to a outer air, to give a back air pressure on the trap and lessen the danger from siphonage. obviously, such a pipe from every trap greatly complicates a plumbing system, and trap vents are now omitted on much of the best work in the United States. Regarding the omission of both main traps and trap vents it should be said that there is little need for them on well designed and built house and street sewerage systems, because the wastes are speedily removed and in well-venti lated sewers the air is comparatively good.