This section is from the book "Mechanics Of The Household", by E. S. Keene. Also available from Amazon: Mechanics Of The Household.
Water closets are made in a great number of styles to suit the architectural surroundings and the various conditions under which they are to be used. Many forms of water closets are manufactured to conform to special conditions, but those commonly used in the bathrooms of dwellings are of three general types. The mechanical construction of each is shown in the following drawings, Figs. 101, 102 and 103 showing respectively in cross-section the principle - of operation of the washout closet, the washdown closet and the siphon-jet closet. Washout Closets. - This type of closet has in the past been used to a very great extent. It does not perform the work it has to do, so perfectly as the others, because the shallowness of the water in the bowl allows it to give off odors, and because it is difficult to keep clean. The action of the closet is as follows: When the closet is flushed the water enters the rim at A, and the greater portion of it is washed downward at B to dislodge the contents of the bowl. A lighter flush is sent through the openings in the side, which serves to wash the entire surface. The direction of discharge is forward, where it dashes against the front of the bowl and then falls into the trap. The only force received to carry the water to the trap is from falling through the distance from the point where it strikes the front. The flushing action is obtained from the use of a large volume of water. As the discharged matter is dashed against the front of the bowl, the flushing action of the water is not sufficient to remove all the stains; the result is an accumulation of filth. This part of the bowl is out of sight; hence, it is seldom kept clean. The name washout comes from the action of the water to wash out the contents of the bowl.

Fig. 101. - The wash-out closet.

Fig. 102. - The wash-down closet.

Fig. 103. - The siphon-jet closet.

Fig. 104. - A poor design of wash-down closet.
As shown in Fig. 102, the action of this closet is to wash the contents of the bowl directly down the soil pipe. The depth of the water at A is much greater than at the corresponding point in the washout closets; as a consequence fecal matter is almost submerged. The main objection to this closet is that it is noisy. Fig. 104 shows another form of wash-down closets. This closet is open to objection because of faulty design; the part A is difficult to keep clean because of its shape.
 
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