48. Urinals are made of two styles, round and lipped. The latter are to be preferred, because they catch drippings betterthandothe round ones.

Urinal waste pipes are likely to become choked from organic matter which is deposited by the urine passing through them; and to flush them properly a considerable quantity of water is necessary.

The flushing pipe is usually connected at the top of the urinal, as shown at A, in Fig. 25. The flushing rim i?of the urinal C distributes the water so that the whole interior surface is washed.

Fig. 25.

Urinals which have a strainer over the outlet should be provided with an overflow as at D. It is very difficult to prevent urinals from emitting offensive odors, unless they are provided with a local vent of sufficient size to draw a continuous current of air down through the outlet of the bowl.

49. If water is so scarce that a continuous flush cannot be permitted, the automatic arrangement shown in Fig. 25 may be used. The supply valve E is of the self-closing variety, and the valve stem projects upwards against a hinged platform or treadle F. To use the urinal, a person must stand upon the treadle, and that yields under his weight sufficiently to open the valve. The water flows as long as the treadle is depressed, and ceases as soon as the weight is removed from it. A small part of the water is used to flush the treadle box and remove the drippings that may fall into it. The waste pipes G and I and trap J should be not less than 1 1/2 inches in diameter. The waste and trap from treadle box should be 1 1/4 inches in diameter. The waste pipe from the treadle box should be vented by a 1 1/4-inch pipe L, which should join the principal vent pipe K. The diameter of K should be not less than 1 1/2- inches. The local vent or ventilating pipe M should be 2 inches in diameter, and care must be taken to get a good draft of air through it. The stopcock N is used to shut off the water supply.

Attachments which open the supply valve and allow the water to run, are sometimes fastened to the door of the stall in which the urinal is enclosed, so that a given quantity of water will be discharged into the urinal every time the door is opened. Consequently, the urinal will be flushed before and after use. The door is closed by a spring or weight.