The body of clean-out ferrules (Fig. 7) is made of brass or cast-iron; fittings of either metal may be used, although cast-iron clean-out ferrules are the better. They are thicker, heavier, more rigid and easier to make tight than brass ferrules, and not so easily bent out of shape when being calked. The plug for clean-out ferrules should be of brass, at least one-quarter inch thick, and the engaging parts have at least six standard iron pipe threads; also they should have a square or hexagonal nut, at least one inch high and one and one-half inches in diameter, so that the nut can be firmly gripped by a wrench when necessary to tighten or unscrew the plug.

Fig. 7

Fig. 8

Clean-out ferrules up to five inches in diameter should be the full size of the pipes, and/should be so located in a system of house drains that the interior of the entire system, from the street sewer to the farthest branch, will be accessible. A full sized clean-out ferrule should be calked in the end or branch hub of a Y fitting placed in the house drain where it enters the building (Fig. 8) so in case of stoppage in the house sewer a rod can be pushed clear through the house sewer to the street sewer to dislodge the obstruction. In waste pipes from kitchen or scullery sinks, or other fixtures in which large quantities of grease are emptied, clean-out ferrules should be provided about every ten feet along horizontal runs through which to remove grease that when chilled adheres to the sides of the pipes to such an extent as to sometimes completely close the bore. Clean-out ferrules should also be provided in all main drains, yard, area or rain leader traps, but are never required in vertical stacks of pipes. Before a clean-out plug is screwed into its ferrule the threads should be lubricated with graphite. This is to prevent the threads from corroding and sticking when the plug is to be removed.

Fig. 9