Special care must be exercised to see that there is no opportunity for dirt to collect in the basement drops. Above is shown a common wrong way and two possible right ways.
FIG. 55. STANDARD DURHAM RECESSED DRAINAGE FITTINGS GENERALLY USED IN VACUUM CLEANING INSTALLATIONS.
While the utmost care should be taken to prevent stoppage of the pipe lines these stoppages are likely to occur in the best-constructed lines and ample clean-out plugs should be provided for the removal of such stoppage. Brass plugs are the most serviceable for this purpose, as they are easily removed when necessary and can usually be replaced air tight.
The brass clean-outs, while most satisfactory, are costly when installed in large sizes. Equally satisfactory results can be obtained at a lower cost by using 2-in. diameter plugs on all lines 2 in. and over in diameter.
FIG. 56. FRICTION LOSS IN PIPE LINES.
Matches are perhaps the most frequent cause of stoppage in pipe lines. Stoppage from this cause can be largely avoided by the use of pipe of sufficient size to permit the match to turn a complete somersault within the pipe whenever it catches against a slight obstruction or rough place in the pipe or fittings. A 2-in. diameter pipe is just large enough to permit this and smaller sizes of pipe should be avoided whenever possible.
Pipe Friction.
—The friction loss in piping follows the same law as that in hose lines and is easily computed by use of the chart ([Fig. 56]), which is constructed on the same general principle as the chart of hose friction ([Fig. 48]). The directions for use of the hose chart apply to the pipe chart. In computing this chart the actual inside diameter of the commercial wrought-iron pipes have been used instead of the nominal diameters, resulting in an increased capacity for all sizes except 2¹⁄₂-in. which is less than the nominal diameter.