Amount Of Flush

No water-closet, however good it may be, will be satisfactory unless it is adequately flushed. The dribble of water which was formerly admitted to the basin through a small pipe was insufficient to cleanse the basin, and was absolutely useless for flushing the trap, soil-pipe, and drain. In the case of valve-closets, where the basins retain a considerable quantity of water, the soil may be carried through the trap by the rush of this water alone, but other closets require an adequate supply of water discharged in sufficient volume and at a sufficient velocity. In order to prevent waste of water, public water-companies almost invariably insist on some kind of "water-waste preventer" being fitted to every closet, so that no more than a stipulated quantity of water can be used at each flush. The limit is usually fixed at two gallons and in such cases a closet and trap must be selected which will be thoroughly cleared by the proper discharge of this quantity of water.

Experiments have shown that, while this quantity is sufficient to clear a good wash-down closet and trap, it is not sufficient to carry the soil through a moderately long branch-drain and through the disconnecting trap placed between the house-drain and sewer, nor is it sufficient to carry the soil through the trap of a wash-out closet in every case. Eighteen tests were made by Dr. Charles Porter, of Stockport, with a well-known wash-out closet. In six tests a 3-gallon flush was used, and although the closet-trap was cleared in every case, the 4-in. disconnecting trap was cleared only twice; twelve tests with 2 1/2-gallon and 2-gallon flushes showed that these were utterly inadequate-in eight cases the closet-trap was not cleared, in five the drain was not cleared, and in every case the disconnecting trap retained a portion of the soil. The results of tests with a wash-down closet were much better; the closet-trap and drain were cleared by a 2-gallon flush, but in no case was this sufficient to clear the 4-in. disconnecting trap. A 2 1/2-gallon flush was not very much better, but three gallons invariably cleared the closet, drain, and trap. In all cases the drain was 47 ft. long with a gradient of 1 in 40, and had one rounded right-angle bend. With a 6-in. drain (gradient 1 in 60) and a 6-in. disconnecting trap, even a 6-gallon flush cleared the trap only twice in four tests. These and other experiments show clearly that the limit of two gallons is too low, and there is a growing feeling that all water-companies ought to be compelled by law to follow the example of Brighton and some other authorities in allowing at least three gallons for flushing a water closet. The extra cost of a 3-gallon cistern is very small, and this size ought to be used in every case where the regulations admit or where the water supply is private. Many siphonic closets require a 3-gallon flush to ensure siphonic action, and the large water-areas of some wash-down closets also render an ample flush desirable.

Flushing Valves

It was at one time the practice to supply water-closets through a valve (either simple or regulating) placed in the cistern used for storing drinking water, but this arrangement is now almost universally condemned by sanitary authorities, and ought never to be adopted. Valve-closets are often supplied through some kind of valve fitted on the supply-pipe under the seat of the closet. The simplest forms are the "Stool" and "Cottage" valves, but as these continue to supply water as long as the handle is held up, they are not as a rule approved by water-companies. Regulating valves were therefore introduced, which close automatically after the passage of a certain quantity (usually 2 gallons) of water, whether the lever is held up or not. All these valves are apt to get out of order, and water-closets are now generally supplied directly from a separate cistern having an inlet controlled by a ball-valve, so that the supply is automatically shut off when the cistern is full.