39. The purpose of a flushing apparatus is to thoroughly detach and remove all excreta, etc., from a water-closet bowl and drive it through and beyond the trap. If the excreta can be driven out of the water-closet branch into the main soil pipe, or main drain, it should be done, provided the water is abundant and not expensive; but it should invariably be driven out of the trap.

The efficiency of a flushing apparatus can be readily tested by coloring the water in the closet bowl with ink and throwing in some pieces of crumpled paper. Then start the apparatus. The flush may be considered satisfactory if no trace of ink or paper remains in the bowl, and if the trap and basin contain a proper quantity of clean water after the flush is over.

To secure a proper flush, a flushing tank should contain from 4 to 6 gallons of water, and it should be elevated at least 6 feet above the water-closet bowl.

40. A common variety of flushing tank is shown in Fig. 21. The valve A is pulled open by means of the lever E and hand chain G. The overflow B opens into the flush pipe D beneath the seat of the valve. The water rushes down the flush pipe only while the valve A is held open.

41. With this construction, the amount of water sent down may be too little to do the work properly, or the water may be wasted by holding the valve open longer than is necessary. To remedy this defect, the siphon tank is used.

Fig. 21.

The construction of the siphon valve is shown in Fig. 22. It consists of an inner tube B and outer tube C which are united at the top by an air-tight cap D. The inner tube is provided with a rubber ring R, which forms the valve, and is seated upon the seat ring S. The two tubes thus form a siphon, the inner tube being the long leg. It is started into operation by lifting the valve off its seat. The water rushes down the flush pipe, draws the air out of B, and quickly fills both B and C with water. The valve is dropped back to its seat, and the discharge continues through B and C until the level of the water falls below the lower end of C. Thus, if the valve be opened only a moment, or long enough to start the siphon, the tank will empty to the same point and the same amount of water will be delivered upon every occasion.

Fig. 22.

The device shown in Fig. 21 can be easily modified to accomplish the same result. The overflow pipe B may be prolonged and bent over, as shown by the dotted lines, thus forming a siphon.

42. Another variety of flush tank gives a large flush first and a smaller one immediately afterwards, the purpose of which is to properly fill the water-closet bowl and seal the trap. This is called an after-flush tank, and its construction is shown in Fig. 23. The tank is divided into upper and lower chambers E and H. The valve A is made about 4 inches in diameter, and when it is opened, it passes water much faster than the flush pipe D can discharge it. The surplus fills the chamber H. When A is closed, the large flush ceases and the lighter flow continues until the chamber H is emptied. F is the overflow for the chamber E.

Fig. 23.

43. Flushing tanks may be dispensed with in some eases, by using a closet valve upon the service pipe, which, when opened, will remain open for a short period of time, and will automatically close itself, after permitting a quantity of water to pass which is sufficient to properly flush the bowl; this arrangement, however, is not as desirable as the overhead tank.

Flushing tanks for water closets and urinals are commonly made of wood and are lined with copper. They are also made of cast iron, and should be porcelain lined, enameled, or galvanized, to prevent rusting. Paint is not a sufficient protection for the inside of a tank.

44. Water closets should never, if it can be avoided, be supplied with water direct from city mains. They should in all cases be flushed by small overhead tank arrangements, unless exposed to frost, as the waste of water is thus largely prevented.

45. Periodical Flushing Tank

Periodical Flushing Tank. This apparatus is designed for automatically flushing urinals, etc. at regular intervals. The form shown in Fig. 24 is called a tilting tank. The tank A is divided by a partition into two equal chambers. It rocks upon an axle B, and thus brings either chamber under the supply cock C. As the chamber fills, the center of gravity gradually changes until it passes over the axle B, when the tank tilts over, emptying one chamber and bringing the other into position for filling. The water being emptied suddenly, a rapid flow is produced, which is well suited for flushing purposes.

The bottom of the outer tank or receiver D should preferably be round, that the water may flow more rapidly and more steadily down the outlet pipe E, Sheet-metal shields F prevent water from splashing over the sides when the tilting tank A is discharged.

Fig. 24.