_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.
_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.
=Yard Closets.=--In many old houses the water-closet accommodations are placed in the yard. There are two forms of these yard closets commonly used--the school sink and the yard hopper.