This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
The various fixtures have been taken up, together with the different kinds of traps which are used in connection with them, and also the general methods of making the various connections for waste and vent. We will next take up some of the points in regard to the manner of running and supporting the different pipes, together with the proper sizes to be used under different conditions.
The waste pipes of necessity contain more foul matter and therefore more harmful gases than the fixtures, so that especial care must be taken in their arrangement and construction. It is advisable to keep all piping as simple as possible, using as few connections as is consistent with the proper working of the system.
The fixtures on each floor should be arranged to come directly over each other, so as to avoid the running of horizontal pipes across or between the floor beams. The sizes of pipes commonly used require such a sharp grade that there is not sufficient space, in ordinary building construction, between the floor boards and ceiling lath below for horizontal runs of much length. One soil pipe is usually sufficient for buildings of ordinary size, and in cold climates is necessarily carried down inside the building to prevent freezing. One or more waste pipes from sinks, bathtubs, etc., are usually required in addition to the soil pipe. These may be connected directly with the soil pipe (through traps), if located near it, or may be carried to the basement vertically and then joined with the main drain pipe inside the running trap. These should also be placed on the inside wall of the house, and, if necessary to conceal them, the boxing used should be put together in such a manner that it may be easily removed for inspection.
The main soil pipe should also be placed where it can be seen, so that leaks may be easily discovered; it is commonly run along the basement wall and supported by suitable brackets or hangers. If carried beneath the cellar floor, it should run in a brick trench with removable covers. In running all lines of pipe, whether vertical or horizontal, they should be securely supported and, in the case of the latter, properly graded. Some of the various kinds of hangers and supports used are shown in Fig.. 79 and 80. The grade of the pipes should be as sharp and as uniform as possible. The velocity in the pipes should be at least two feet per second to thoroughly clean them and prevent clogging. Generally speaking, the pitch of the pipes should not be in any case less than 1 foot in 50. In running lines of soil pipe, it is best to set the joints ready for calking in the exact positions they are to occupy and resting upon the supports which are intended to hold them permanently. In this way there is less liability of sagging or loosening of the joints after calking. In the running of vertical pipes, care should be taken to have them as straight as possible from the lowest fixture to the roof.
It is very necessary that the pipes be given such an alignment that the water entering them will meet with no serious obstructions. Where vertical pipes join those which are horizontal, they should be given a bend which will turn the stream gradually into the latter, thus preventing any resistance and the resulting accumulation of deposits. Horizontal pipes may be joined with vertical pipes without a bend, as the discharge will be sufficiently free without it. However, it is customary to use a Y or T branch, giving a downward direction to the flow when connecting a closet or other fixture where there is likely to be much solid matter in the sewage. Offsets should always be avoided as far as possible, as they obstruct the flow of both water and air.
The most important requirements in the case of discharge pipes are that they carry away the waste matter as thoroughly as possible without stoppage of flow or eddying, and that they be well ventilated. In order to accomplish this they must be given such sizes as experience has shown to be the best. When water having solid matter in suspension half fills a pipe, the momentum or force for clearing the pipe will be much greater than when it forms only a shallow stream in one of a larger size, so that in proportioning the sizes of soil pipes and drains care must be taken that they are not made larger than necessary, for if the stream becomes too shallow the pipes will not be properly flushed and deposits are likely to accumulate. The amount of water used in a house of ordinary size, even when increased by the roof water from a heavy rain, will easily be cared for by a 4-inch pipe having a good pitch. While a pipe of this size would seem to be sufficient, it is found by experience that it is likely to become clogged at times by substances which through carelessness find their way into the drain, so that it seems best to use a somewhat larger size. For city buildings in general, it is recommended that the main drain should not be less than 5 or 6 inches in diameter, and in ordinary dwelling houses not less than 5 inches. The vertical soil pipes need not be larger than 4 inches, except in very high buildings.
Waste pipes may vary from 1 1/4 inches to 2 inches. The waste from a single bowl or lavatory should be 1 1/4 inches in diameter, from a bathtub, kitchen sink or laundry tub 1 1/2 inches, from a slop sink 1 3/4 inches. Smaller pipes should never be used. In laying out the lines of piping, provision should be made for clearing the pipes in case of stoppage. Fig. 81 shows how this may be done. Clean-out plugs are left at the points indicated by the arrows, so that flexible sticks or strips of steel may be inserted to dislodge any obstruction which may occur.
The fresh-air inlet to the main drain pipe has already been referred to. This should be located away from windows, where foul air would be objectionable; in cities they may be placed at the curb line and covered with a grating. Sometimes they are arranged as shown in Fig. 82. The opening is made in the usual way, and a hood placed over the inlet, and a pipe leading from this is carried through the roof. When the circulation of air is upward through the main soil pipe the opening acts in the usual way, that is, as a fresh-air inlet, but should there be a reversal of the current from any reason, which would discharge foul air from the sewer, it would be caught by the overhanging hood and carried upward through the connecting vent pipe to a point above the roof. A general layout for house drainage is shown in Fig. 83.