Fig. 25 shows a section of the flue thus brought out. The wall is two bricks thick, the flue a, is 9 inches in diameter, d is the cast-iron flue, and another, e, shaped like a funnel, is placed behind it, to collect the soot and water, and pass it off through the pipe h. The cistern is partly within the walls and partly covering the two flues. It is not necessary that the water in the cistern should supply the spray: that might be done by a separate pipe with a tap to turn off and on as desirable; b is the moveable pedestal covering the whole.
The adaptation of this simple contrivance to any kind of domestic chimney-flue is not a very difficult operation. It is only necessary to take out the brickwork in front of a flue of a height of 4 to 5 feet, and then introduce the iron flue, gathering up the brickwork beneath it; the section, fig. 25, supposes the iron flues to be in an external wall; should it be required in a party wall the soot goes off at g g, to be conveyed outside the building in the nearest way; doors are provided for the purpose of sweeping; any down
Fig. 25.—Section of the flue pedestal.
draught of air in the chimney might expend itself in the soot flue, and the smoke having passed the spray could not return. The spray of water should be equal to the whole width of the flue, and proportioned in strength to the work it has to do; the smoke from a whole group of flues might be conducted to one powerful spray, one upper flue or chimney would then suffice for the roof, while the soot and flues in any number might be formed into one before passing to the sewer.
The pipe h, shown in fig. 25, would not form an open communication with the sewer; it would be supplied with a flap-cover or drain-eye, like the common house drain at its extremity. This would open only when sufficient water and soot was behind it, and close when it was passed. It would not require sweeping, the water keeping it clear. It should have another kind of drain-eye to that at present in use, the lid, or flap of which is hinged from the top, the soot floating on the surface of the water, would require the flap to open from below. Fig. 26 shows the kind of drain-eye that would be required.
If it was not for the difficulty of the present form of drain-eye to our houses, the soot flue might discharge its contents into the house drains at once, below the trappings; there is probably no absolute necessity at all for drain-eyes at the termination of house drains, their use is to make precaution doubly sure, to prevent the rising of the gases from the sewer, and to keep out the rats, to prevent them, by getting through the traps, from entering the house.
Fig. 26.—Drain-eye.