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The quality of the galvanizing may be observed by bending the pipe at an ordinary temperature, to an easy bend. If the galvanizing is good it will remain intact. Galvanized-iron pipes are liable to be quite brittle, but this brittleness does not seem to affect the durability of the pipe. The ductility of galvanized-iron pipes is less than that of black iron pipes, and sometimes is so low that if the pipe is bent successfully it cannot be bent back without breaking.
In black wrought-iron pipe the welded seam that runs the whole length of the pipe should be scarcely visible, and the pipe should have a smooth external and internal surface. The pipes should be straight and the threads cut clean.
Mild steel pipe is the same in dimensions as wrought-iron pipe, but is softer, more easy to cut and thread, and is more durable.
Wooden pipes should be examined chiefly for knots, splits, and cross-grained wood, as these weaken the tube.
Cast-iron soil pipes should be examined for sand holes, flaws, and splits in the pipe. A fracture can be detected by tapping the pipe with a chisel or small hammer. If the pipe is sound, it will ring clearly when struck; but if cracked, it will give a dull, harsh sound. Sometimes the core will shift when the pipe is being cast, particularly if the pipe is cast horizontally, in which case the core is liable to rise in the middle. This will cause the metal to be thicker on one side than the other of the pipe. Irregularities in thickness can be detected by irregularities of the sound when rapped with a hammer at various points.
Flaws, or places where the metal has not flowed together and become properly united, can be detected by sounding the pipe with a hammer, or by its appearance, if the flaws are external.
Earthen drain pipes are liable to warp and twist in firing. They should be examined for an equal caliber, smooth-glazed internal and external surface, and particularly for cracks around the back of the socket and irregularities within the socket. Pipes having broken or crooked sockets should be rejected.
Fittings for wrought-iron and brass pipe should be inspected for sand holes and flaws; the screw threads should be deep and full. Fittings for cast-iron drain pipes should be examined for sand holes, splits, and other flaws, and for lumps and other obstructions to the free flow of sewage.
Fittings for earthen pipe should be examined for irregular ities in cross-section, or caliber, for cracks, protruding pieces of salt glaze, abrupt turns, etc. The sockets should be examined to see that they are round and of proper depth. All defective fittings should be rejected.
The drainage system in a building usually consists of a main house drain, stacks of soil, waste, and vent pipes, short branch connections, rain leaders, and yard and area drains. The vent pipes are a necessary accompaniment. The various parts are shown and named in the isometric illustration, Fig. 1.
Main-drain and rain-water traps in a cellar may advantageously be arranged in a brick manhole, as shown in Fig. 2.
The main-drain trap a is provided with two brass screw-cap clean-outs flush with the floor of the manhole. The rainwater leaders discharge through the pipe b into a rain-water trap c, which is set a little higher than the main-drain trap, so that the rain water may discharge into the sanitary T fitting d on the fresh-air inlet pipe e. Each underground trap is thus accessible and can easily be cleaned at any time.
DRAINAGE SYSTEM DETAILS.
Sizes of Pipes.-House sewer and drain pipes must be at least 4 in. in diameter, where water closets discharge into them. Where rain water discharges into them, the house sewer and the house drain up to the leader connections should be in accordance with the table "Size of Pipe for Drainage." The various soil, waste, and vent pipes should correspond in size to that given in the table "Least Sizes of Soil, Waste, and Vent Pipe."
SIZE OF PIPE FOR DRAINAGE.
For fixtures other than water closets and slop sinks and for more than 8 stories, vent pipes may be 1 in. smaller than above stated.
All vent pipes that pass through the roof should be increased one size through and above the roof to allow for ice accumulations inside. In no case should any of these pipes be less than 4 in. in diameter, except in mild climates. Care should be taken to prevent the use of the old-fashioned, cast-iron vent caps. If the open end must be protected, wire baskets may be used.
The fresh-air inlet should be of the same size as the drain, up to 4 in.; for 5" and 6" drains, it should not be less than 4 in. in diameter; for 7" and 8" drains, not less than 6 in. in diameter; and for larger drains, not less than 8 in. in diameter. The fresh-air inlet orifice should have an area equal to that of the pipe.
LEAST SIZES OF SOIL, WASTE, AND VENT PIPE.
Name of Pipe.
Main and branch soil pipes
Main waste pipe
Branch waste pipes for kitchen sinks
Soil pipe for water closets on 5 or more floors
Bath or sink waste pipe
Basin or urinal waste pipe.
of 2 tubs.
Wash tubs, 14" waste pipe and 2" trap for set
Waste pipe for a set of 3 or 4 tubs
Vent pipe for other fixtures on less than 7 floors
Fall for Drain and Waste Pipes.-The fall of a drainage system should be so arranged that the velocity of the flow obtained will be not less than about 275 ft. per min. This velocity can be closely approximated by pitching the pipes as follows:
GRADES FOR DRAIN PIPES.