Among closets of this type I mention Jenning's closets, the Demarest closet, Mott's "Hygieia" closet, Moore's closet, Zane's "Sanitary" closet, the California "Perfection" closet. Myers' Gale closet, Myers' China closet, the Hartford Glass closet, Myers' egg-oval water closet, Smith's "Arizona" plug water closet, Pearson's Twin basin closet, Smeaton's trapless water closet, Smeaton's "Eddy-stone " closet and others.
The characteristic detail of all these (see Fig. 4 C) is the plunger closing the outlet of the bowl, which is placed at the side of the closet. The foul matters drop into a large body of water in the bowl, are therefore partly deodorized and easily removed from the bowl. By lifting the plunger the contents of the bowl are rapidly discharged into the soil pipe, and the rush of the water, leaving the bowl, is so great as effectually to drive all matters through the dip of the trap. The latter must be efficiently protected against siphonage, which is more likely to occur with plunger closets than with the pan, valve, or hopper closets. The danger with closets of this class lies in the fouling of the plunger chamber. Waste matters and paper may stick to the seat of the plunger or to its sides; the outlet will then be imperfectly closed, allowing the water to leak out of the bowl. Closets having a small plunger chamber are the better ones, not only because they will be cleaner, but because with large chambers the waste of water must necessarily be large.
Plunger closets flushed by a special cistern require no supply valve nor float in the plunger chamber, which, therefore, may be of smaller dimensions, and hence are superior to other closets of this type.
In some plunger closets a special spray arrangement is intended to wash the sides of the plunger and its chamber at each use of the closet, but, while it may be efficient, it tends to complicate the closet. The better closets of this class provide the top of the bowl with an improved flushing rim, or wash the sides of the bowl by an effective fan or water-spreader. In order to provide for an overflow the plunger is sometimes made hollow, and when trapped it is so arranged that the water forming a seal is renewed at each flush. Otherwise it is liable to evaporate and this is especially dangerous with plunger closets that are trapless.
Trapless plunger closets are not safe for same reasons as stated for trapless valve closets.
In some closets an independent overflow is arranged. Most plunger closets are flushed by a valve, worked by a float in the plunger chamber. These valves are not always reliable, especially under varying pressures, and it is much better to flush these closets from a special cistern.