A more recent form of siphon-closet dispenses with the jet, and obtains the filling of the waste-pipe beyond the trap, essential to siphonic action, by making a sharp bend in it (Fig. 21), so as to impede the current momentarily, and throw the water back on itself, without diminishing mate Dececo closets rially the size of the pipe. This answers the purpose of setting up siphonic action perfectly, and the fact that the closet has no jet-tube to freeze and burst, and can be entirely cleared of water by sponging out the basin, is often a great advantage.

Fig. 21.

Another type of closet, which formerly enjoyed a rather undeserved popularity, is the "washout," or, as it is often called, from the trade-name of the best known pattern, the "Brighton" closet (Fig. 22). This has a shallow basin, with flushing-rim, so arranged as to drive the water standing in the basin either backward or forward, according to the pattern used, into a trap, which is formed in the earthenware under the basin. In some forms of this closet the trap is nearly inaccessible, and in all it is practically out of sight; so that, even if the basin is clean, the hidden trap may be very foul, and, when in that condition, sends its odors freely into the room. With a sponge, tied to a stout wire, the trap can be easily cleaned, if necessary, so that a washout closet, properly cared for, is satisfactory enough; but it is better, in plumbing appliances, that the need of cleaning should be manifest to the eye before it makes itself known to the nose.

Washout-closets.

Fig. 22.

Nearly all modern water-closets can be had with " local-vent" connections, by which air may be drawn from the basin of the closet, directly under the seat, to some heated flue. In most cases these local vents, if the closet has been ordered with them, are simply plugged up by the plumber; but it is very desirable to connect them, by lead, copper, or other pipe, with some flue that can be warmed. The range-flue is usually chosen, and is the most suitable, if its draught is goodenough not to be checked by the vent-pipe. Although the local vent is small, being, for house water-closets, from two to three inches in diameter, the slow current through it does much to purify the air of the small rooms in which water-closets are placed.

Local vents

As a rule, water-closets in dwelling-houses receive their supply of water from a copper-lined cistern, or tank, usually supported by brackets on the wall above the closet, into which the water flows through a small pipe, and a ball-cock, arranged with a float, which shuts the water off when the cistern is full; while a cistern-valve, which can be lifted by pulling a chain or rod attached to a lever, allows the water to flow out rapidly for flushing. The cistern is usually provided with an overflow connected with the flush-pipe, so that, if the ball-cock fails to act properly in shutting off the water, the surplus will escape through the water-closet to the drain, instead of overflowing on the floor.

Every plumbing fixture must have a trap of some kind to prevent foul air from coming back from the drain through its waste outlet. In its simplest form a trap is merely a downward bend in a pipe, so deep that the upper wall of the pipe dips into the water held in the bend, the extent to which it dips being known as the depth of the seal. With slight modifications this is the trap (Fig. 23) most commonly used for wash-basins, water-closets, and other apparatus where grease is not likely to get into the waste.

Fig. 23.

Water-closet cisterns.

Traps.

For kitchen sinks, pantry sinks, and wash-trays the plain dip, or S trap would soon be choked with grease or sediment, so that it is usual to furnish these with a "round trap," consisting of a lead cylinder, from four to six inches in diameter, with an inlet-pipe near the bottom, and an outlet-pipe near the top (Fig. 24). The cylinder is large enough to accommodate a considerable accumulation of grease, without cutting off entirely the flow of water through the trap. To clear out the grease, when necessary, round traps are always fitted with brass trap-screws, at least four inches in diameter, this being the smallest size that will admit the hand; and it is not a difficult matter to unscrew the trap-screw with a wrench, dig out the white mass of solidified grease, and close the opening again. For baths, although accumulations of grease are not to be feared, it is very common to use a round trap, set in the floor, with the trap-screw flush with the surface of the floor, and either left exposed, or covered with a nickelled plate. As the waste outlet of a bath is necessarily near the floor, this form of trap is more conveniently connected than an S trap would be, while the four-inch trap-screw in the floor makes it easy to recover rings, precious stones, and other articles which are frequently lost in baths. The stones from rings also often fall into basin-wastes, but as the basin trap is always, in a modern house, high above the floor, the small screw which is generally set in the bottom of S traps, as shown in Figure 23, can be removed, when everything in the trap will fall into a dish or pail previously set underneath to receive it. Water-closets often have their trap formed in the porcelain itself, and, as the waterway is always large enough to admit the hand, they are accessible for cleaning or for recovering lost objects, without trap-screws.

Fig. 24.

Round traps.

An inspection of the trap under any plumbing fixture will show the inlet-pipe and outlet-pipe, but, in most cases, a third pipe will be found, extending upward, either from the trap itself, or from the outlet-pipe, near the trap. This pipe is the back vent, and is intended to prevent the removal of the trapping-water by siphonage. The action of a siphon water-closet, by which, as soon as the waste-pipe beyond the trap is filled with water, all the contents of the basin are drawn over by atmospheric pressure, shows what may happen in any S trap, or in a round trap partly filled with grease, if the bore of the outlet pipe should become completely filled with water, as may easily happen if a slight obstruction Back vents should momentarily check the flow. In order to prevent the loss of the trapping-water in this way, and the consequent opening of a passage for sewer-gas through the trap, an air-pipe, or back vent, is carried from the outlet side of the trap to a main air-pipe, through which air can be drawn to supply the vacuum caused by the descent of a solid column of water, without disturbing the sealing-water of the trap.