(1) There being a number of parts and mechanical contrivances, they are liable to get out of order. (2) The bowl is set into the container and cannot be inspected, and is usually very dirty beneath. (3) The pan is often missing, gets out of order, and is liable to be soiled by adhering excreta. (4) The container is large, excreta adhere to its upper parts, and the iron becomes corroded and coated with filth. (5) With every pull of the handle and pan, foul air enters rooms. (6) The junctions between the bowl and container, and the container and trap, are usually not gas-tight. (7) The pan breaks the force of the water flush, and the trap is usually not completely emptied. _Valve and Plunger Closets_ are an improvement upon the pan closets, but are not free from several objections enumerated above. As a rule, all water-closets with mechanical parts are objectionable. _Hopper Closets_ are made of iron or earthenware. Iron hopper closets easily corrode; they are usually enameled on the inside. Earthenware hoppers are preferable to iron ones. Hopper closets are either long or short; when long, they expose a very large surface to be fouled, require a trap below the floor, and are, as a rule, very difficult to clean or to keep clean. Short hopper closets are preferable, as they are easily kept clean and are well flushed. When provided with flushing rim, and with a good water-supply cistern and large supply pipe, the short hopper closet is a good form of water-closet. The washout and washdown water-closets are an improvement upon the hopper closets. They are manufactured from earthenware or porcelain, and are so shaped that they contain a water seal, obviating the necessity of a separate trap under the closet. [Illustration: FIG. 25. LONG HOPPER WATER-CLOSET. (GERHARD.)] [Illustration: FIG. 26. SHORT HOPPER WATER-CLOSET. (GERHARD.)] [Illustration: FIG. 27. STYLES OF WATER-CLOSETS.] _Flush Tanks._--Water-closets must not be flushed directly from the water-supply pipes, as there is a possibility of contaminating the water supply. Water-closets should be flushed from flush tanks, either of iron or of wood, metal lined; these cisterns should be placed not less than four feet above the water-closet, and provided with a straight flush pipe of at least one and one-quarter inch diameter. The cistern is fitted with plug and handle, so that by pulling at the handle the plug is lifted out of the socket of the cistern and the contents permitted to rush through the pipe and flush the water-closet. A separate ball arrangement is made for closing the water supply when the cistern is full. The cistern must have a capacity of at least three to five gallons of water; the flush pipe must have a diameter of not less than one and one-quarter inch, and the pipe must be straight, without bends, and the arrangement within the closets such as to flush all parts of the bowl at the same time. [Illustration: FIG. 28. FLUSHING CISTERN.]