562

Traps for Drains, Sfn.

[Book V.

France before being known in England. Those which he has figured arehowever on the ancient plan, without traps, and such are still to be foundin oriental cities. They are not to be compared with the modern ones.(See L’Art du Menuisier, folio edit. 1770, PI. 69 ; Gell’s Pompeiana; ADissertation on Places of Retirement, Lond. 1751 ; Fryer’s Travels inIndia and Persia , Lond. 1698.)

Devices for preventing the ascent of offensive vapors from sinks, sewers)drains, &c. are named traps. As these are simple in construction, andapplicable under all circumstances, and yet are little known, we haveinserted a sketch of a few of the most common. They are all modifica-tions of the same principle.

No. 278. No. 279. No. 280. No. 281.

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A A represent a floor or covering of a sink or sewer, and the object isto discharge refuse water or slops of any kind into the latter withoutallowing currents of air to rise through the passage. No. 278 is a leadenpipe bent at one part into the form of a letter S, which part constitutesthe trap. One extremity enters the sink, and to the other, which is turnedup perpendicularly, the basin of a wafer-closet, or a common funnel isattached. The flexures of the tube must be such, that whatever liquid isthrown down the basin, a portion will always remain in the bent partbelow so as to seal the passage completely, as shown in the cut. The basinand trap may be placed in a room at any distance above the sink or sewer,provided both are connected by an air-tight tube.

No. 279 is named a D trap, from its resemblance to that letter. It isof the kind generally used in water-closets, for which purpose it is alwaysmade of lead, and about twelve inches long, five wide, and ten or elevendeep. The pipe that enters the sink is soldered to one end and near thetop. The other one to which the basin is attached descends six or seveninches through the top at the opposite extremity of the trap. By thisarrangement water is retained within to a level with the lower edge of thepipe that enters the sink, while the perpendicular pipe dips between oneand two inches below the surface. Hence although impure air in the sinkcan readily ascend into the trap, it cannot enter the tube on which thebasin is placed ; for to do so, it would have to descend through two inchesof the water to reach the orifice of the tube ; and then to ascend throughan equal column within the latter before it could rise into the basin.

No. 280 is a form of trap used over the openings of Street sewers, forwhich purpose they are commonly constructed of stone or brick and linedwith cement. The figure is that of a square box open at top. A pipe isinserted through the bottom at one side to connect it with the sewer. Thispipe Stands about half way up the inside of the box, and above it there isa bent rectangular partition attached at three of its sides to the box, whilethe fourth side extends into the middle and dips two inches below the