There should be sufficient water in the basin to prevent the excreta fouling the sides. It is then not open to the objection of splashing as in the wash-out closet, nor does the flush of water lose its force owing to an intercepting container.

(7) The Self-flushing Closet.

There are various contrivances in existence to render the flushing of the closet independent of the users. One of the old forms is shown in fig. 55, in which weights attached to the back of the seat cause this to tilt up when it is released. At the same time a lever arrangement ensures a flush. An advantage of a self-flushing arrangement is that if used as a urinal or slop-sink the seat cannot be fouled through carelessness.

"Closet of the Century."

A recently introduced and good type of water-closet is the improved "Closet of the Century," a figure of which is reproduced by permission of the inventors.

The service-pipe from the cistern has two connections to the closet-one leading into the basin in the usual manner, the other leading into the top of the long leg of a siphonpipe. The flush from the cistern is thereby divided into two streams-one flushes the basin, the other rushes down the "leg" D, expels the air through the puff pipe E, starts the siphonic action, and empties the basin, which is refilled with clean water by a simple after-flush arrangement in the cistern.

Fig. 56A shows this fitted with a water waste-preventing cistern, and joining the drain beneath the ground level.

Pipe A is taken up to the level of the cistern and left open to admit air to the siphon-leg D, thus preventing siphonage when slops are poured in the basin C. The puff pipe E passes through the wall and is left open as shown. Flushing cisterns or water waste-preventers. To prevent the flushing of closets from being imperfect though carelessness, many plans have been devised for ensuring that once the flow of water is started it will continue until a given volume has been discharged. A good arrangement

is shown in fig. 57. When the plug is removed, water rushes down the pipe and sets the siphon into action; then, even if the plug is replaced, the pressure of the air keeps the water flowing down the siphon until the surface is lowered so much that air is admitted to the short end of the siphon-pipe. Sometimes an air-tube is fixed to the upper bend of the siphon. The volume of water to be discharged can then be regulated by varying the length of the tube. The shorter the tube, the less the volume which flows, as air is admitted sooner. A ball-tap is used for automatically refilling the cistern after discharge.

The cistern may be made of enamelled iron, or of wood lined with lead.

The quantity of water required for flushing a closet is 3 gallons, and to prevent waste it should not exceed 3 gallons. The flushing cistern should be placed 5 or 6 feet above the basin, and in no case less than 4 feet. The

Fig. 57.-FLUSHING CISTERN OR WATER WASTE-PREVENTER.

pipe which carries the water to the W.C. should be 1 to 1 inches in diameter.

Soil-pipes. The pipes which carry excreta and other refuse from water-closets to drains are called soil-pipes. As far as possible they should be placed outside the house

and not exposed to the action of the sun's rays, or they may become bent, or the joints may open owing to expansion. A soil-pipe may be made of lead or iron. Drawn lead pipes are the best kind, but are expensive; seamed lead pipes should not be used. Iron pipes are cheap, but often have a rough surface, which may corrode. If iron pipes are used they should be coated by Angus Smith's method, as for water mains. The soil-pipe should be 3 inches to 4 inches in diameter. If it be wider there is (a) a larger surface to be flushed, (b) a greater area on which deposit may take place, (c) extra cost without extra advantage.

The joints of iron pipes should be caulked with molten lead, but, owing to the difficulty in making a perfect joint, iron should never be used for pipes within the house. Drawn lead pipes should be uniform in thickness, and should weigh from 7 to 8 lbs. per ft. A soil-pipe should always be ventilated by being carried up full bore above the eaves, and should terminate away from all chimneys and windows. There should be as few bends as possible in the ventilator. If it is necessary to deviate from a straight line, rounded curves, instead of right angle bends should be employed.

Trough Closets. These consist of a long metal or earthenware trough placed under a series of closets built side by side. The seats are all arranged over the trough which is partly filled with water and into which the excreta from each falls. The bottom slopes towards the drain, and at the end a ridge is placed to keep the water in the trough. It has been described as an elongated wash-out closet, with a number of separate seats. The upper end is connected with a flushing tank, which may be automatic, or only used when the attendant cleans them out daily. The volume of water required in the cistern depends upon the number of closets connected with the trough, the contents of which are carried by the flush through a trap into the drain. A few bars may be fixed over the opening to prevent unsuitable articles passing into the trap and blocking it, but these should be arranged so that all ordinary matter may pass between.