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and so form a passage for foul air into the house. They ought not to be connected with any part of the water-closet apparatus, trap or soil-pipe, but ought to be carried straight through the wall to end in the open air, being merely provided with a small brass flapper to keep draughts out. The waste, or overflow pipes of cisterns, are frequently carried into the D-traps of closets, in which case foul matters get washed into the inside of these pipes, and foul air from them contaminates the water in the cisterns. This is even a greater evil than the last, and the waste pipes of all cisterns, but more especially those used for the supply of drinking water, should, as stated in a previous lecture, be made to end in the open air.
We come now to valve closets, the numerous varieties of which are modifications of the original Bramah's valve closet. In this the aperture at the lowest part of the basin is closed by a watertight valve, which can be moved in a small valve box, placed immediately below the basin, by means of the pull-up apparatus—the valve box itself being connected below with the trap. Thus, the necessity for the large iron container, so objectionable a part of the pan-closet, is done away with, and its place taken by a small box, in which the valve moves. As, however, the valve is water-tight, provision is made for the overflow of water from the basin, in case the latter should be filled to full, either by slops being thrown into it, or by the water continually running from the supply-pipe in consequence of a leaky valve. The overflow pipe starts from one side of the basin in which holes leading into it are peforated. It is then, as a rule, carried downwards into the valve box, having a small siphon bend on it before entering. The water from the supplypipe, as it enters, is made to flow round the basin by an inner plate, generally made of metal, called the “spreader," or still better, in the improved form of valve-closet by means of a flushing rim. Thus, some of the water at each use of the closet passes through the holes leading into the overflow pipe; the object of this being to keep the siphon on that pipe charged with water, as it is clear that if this siphon is not charged, the overflow pipe ventilates the valve box, that is to say, the space below the valves, and the surface of the water in the trap below into the basin of the closet. Now, as a rule, the siphon trap on the overflow pipe does not remain charged with water, and even if it does, is of little use, for the following reasons—when by the pulling up of the handle the valve is made to move suddenly in the valve box, air from the latter is forced out through the water in the siphon bend of the overflow pipe, as any one can see, who will take the trouble to place a piece of moist tissue paper over the hole in the side of the 'basin leading into that pipe, and then work the handle of the closet. Thus foul air from the valve box is driven into the basin, even when the siphon on the overflow pipe is charged. Furthermore, as the mass of water in
the basin rushes down through the valve box into the trap it carries the air along with it, and when the valve is closed runs out of the valve box, drawing air through the overflow pipe, and displacing the water in the siphon, which is in many cases left quite uncharged. Various remedies have been proposed for this. In Bolding's “Simplex” valve closet a small pipe is carried from the water-supply pipe into the overflow just above the siphon, with the view of supplying water direct to the siphon each time the closet is used. In Jennings' valve closets the overflow is trapped by means of a patent india-rubber ball trap, which is something like a Bower trap upside down. It is constructed so that the overflow water can displace the ball from the end of the water-pipe, and flow away round it, but any pressure of air from the valve box would only cause the ball to fit more closely against the end of the overflow pipe. In the valve closet made by Beard, Dent, and Hellyer, the overflow pipe is made much larger than
usual, and the siphon deeper, so that it holds a larger quantity of water, and at the same time a ventilating pipe is inserted into the valve box, and should be carried through the wall to the outer air. By this means no accumulation of foul air in the valve box can take place, and any air that is drawn into it, while the water is passing through it, comes in through the ventilating pipe instead of through the overflow. It is quite right to ventilate the valve box, but the best way to deal with the overflow pipe is to disconnect it altogether from the valve box, and either carry it through the wall, placing a brass flap on the end of it, or to let it end over the waste pipe of the safe. Indeed, it is hardly necessary to have an overflow pipe at all, as if the basin does get full, all that will happen is that the water will flow over the top of it into the safe and run away. The advantage of this plan is that the existence of a leaky valve is found out immediately, and the disadvantage is that it is liable to wet the end part of