A few years ago, before the need of system-a t i c ventilation of the sewers and soil-pipe began to be felt, and back pressure from the foul sewers forced the sewer gas through the water seal of traps in bubbles, a tight - fitting valve or plunger was felt to be needed in water-closets, and as these closets were at first built without overflows, the valve or plunger did actually seem to perform a real service. Now, however, the circumstances are altered. It is found that an overflow is necessary in these closets, and this overflow passage is rarely provided like the trap with a valve or other mechanical closure. Hence, any gases which could pass an ordinary water seal could pass through these closets by way of the overflow passage quite regardless of and quite as easily as if the valve or plunger in the trap never existed. Moreover, the ventilation of the sewer and soil pipes renders back pressure comparatively harmless, so that the only possible useful office of the valve or plunger is no longer called for.
Fig. 384. Valve Closet.
The same objections to the mechanical seals of water-closet traps which have been described for the smaller fixture traps hold with even greater force with water-closet traps. They cannot be made permanently tight and effective.
The only object of the valve or plunger, therefore, is to retain a certain quantity of water in the bowl to receive the waste matters, and prevent their striking the dry surface of the closet bowl, to which they would adhere, and as this result can now be accomplished equally well without them, and by simpler means, it is obvious that they are utterly superfluous.
The efficiency of the large body of water suddenly emptied from the bowl for flushing out the water-closet and pipes forms a good point in these closets, but it is sometimes partially negatived by the obstruction of the valve and plunger themselves when they are but slightly raised in use or defective through rust and sediment. But this function is equally well performed by simpler and better means.
The receiver or container of the valve and plunger is open to the same objections as that of the pan, differing only in degree, and the overflow passage, not required in the pan-closet, forms a second filth collector, and increases the complexity and cost of the apparatus. The sudden discharge of the larger body of water in the bowl is very liable to empty the trap below by its momentum and siphon action, requiring a special provision for its automatic refilling.
These and other considerations have led sanitarians to differ as to the relative merits of the pan, valve and plunger closets when they were in vogue, though there seemed to be no sufficient reason for such difference. It is only important to analyze the types now because they illustrate forcibly various defects in plumbing appliances which should be strenuously avoided, and they are also interesting to some extent historically.
The Valve Closet.
Valve closets were those which have the outlet of the bowl closed by a movable valve or plate, usually held in place by a lever or spring. Fig. 385 represents a valve closet having the trap below the floor. Fig. 384, a valve closet with a ball in the overflow. These and the type in which the trap is placed above the floor, Fig. 386, have been considered among the simplest and best of their class. All others differ from these merely in slight and comparatively unimportant details. Some valve closets were made without any water trap at all below the valve. These were totally unreliable because no valve has as yet been discovered which is not liable at some time to leak, especially when used in water-closets. Beginning, as before, with
Fig. 385. Valve Closet.
The Flushing. We see, by examining the drawing, Fig. 385, that the cleansing effect of the stream could never reach those parts of the receiver which lie behind the valve and around its hinge, nor any part of the overflow passage. Hence, these parts were sure, sooner or later, to become foul, and they were exactly the parts in which foulness would impede the proper working of the valve and closet, and occasion leakage of the water from the bowl. The receivers of both the pan and the valve closets can be enameled and provided with special cleansing jets, and closets having these improvements have been manufactured, but the overflow passage cannot be so scoured, and I know of no closet in which the attempt to do so has been made. Finely divided waste dissolved in the water and making its way into the overflow passage, as it very frequently did, was bound soon to foul it, and once the deposit began it could not be arrested except by taking the closet to pieces. The extent of surface which cannot be reached by special scouring streams is, therefore, greater in the valve than in the pan closets, and this goes far to offset the advantage it has in the smallness of its receiver.
Fig. 386. Valve Closet.
(b) The valve, like the pan, breaks the force of the flushing stream from the cistern due to head and thus prevents its passing through the receiver and trap in a compact volume, occasioning a total loss of the advantage the water head from the cistern might give and in the better types of closets does give. Here again the valve and pan closets are equally defective.
(c) The same causes for the production of disagreeable noises in flushing exist in both kinds of closets. Most valve closets are superior in workmanship, as well as in price, to the pan closets, but so far as principles of construction are concerned, the valve closet has no superiority over the pan.
(d) To operate the machinery of a valve closet requires more strength than is the case with the pan. It is indispensable that the valve press very firmly against its seat in order to retain and sustain the large body of water in the bowl above it, while no such pressure is evidently required in the pan. To overcome this greater pressure a greater effort is required, so that in this respect the valve closet is inferior to the pan.