To the Boston City Board of Health: -
Gentlemen: - The experiments heretofore made in this country on the siphonage of traps have faithfully shown the siphoning power of those fixtures which are in most common use; and have established the relative strengths of the various forms of best known traps in resisting such power.
You have seen that these experiments have been made and recorded with a degree of care which renders it superfluous to experiment further in the same field. But the fixtures in common use are not the ones which produce the most powerful action of siphonage, and as they are not the only ones used, it is evidently necessary, in order to present a full and correct view of the subject, to supplement the former experiments with others made in a new direction.
The tests have hitherto been made with common pan and hopper closets. It remains to investigate the action of plunger-closets,† and these will serve to illustrate also the maximum power of valve-closets, which we assume to occupy a position, in respect to siphonage, intermediate between plunger and ordinary hopper closets.
*Reprinted from the "American Architect and Building News" of 1884, giving the Author's first public Report on Trap Siphonage and Evaporation, made for the Board of Health in 1883 and 1884.
†The modern siphon jet closets produce an effect of siphonage similar to that produced by the plunger closets in common use at the time of this report.
In the former experiments a single round or pot trap was tested; but since these traps may be made of various sizes, from that which has a body but little larger than that of an ordinary 1½" S-trap, up to the largest whose body measures 8 or 10 inches in diameter, and as their power of resistance to siphonic action is totally dependent on their size, the smallest being but slightly more resistant than an S-trap of equal depth of seal, and the largest being practially unsiphonable, you have recognized the necessity, in order to arrive at correct conclusions as to the efficiency of this trap, of testing them all, and publishing the results in regular tabular form.
The third subject which your Board has given us for investigation is one upon which nothing has to our knowledge as yet been published; but which has, in view of the recent plumbing regulations enacted in different parts of this country, assumed a vast importance. The special ventilation of traps in the manner now customary, induces a current of air over the water-seal, which lowers its level more or less rapidly according to the velocity, temperature, and hygometric condition of the air current.
It is sometimes recommended by sanitary engineers and plumbers to connect the vent-pipe with a heated flue, in order to insure an upward current. Accordingly we have made our tests on trap-ventilation both with heated and with cold flues, and in order to give them as wide an application as possible, we have tested the traps in various positions, and applied the vent-pipes to various parts of the trap.
Finally, we have studied the effect of back pressure on traps, and in this direction as well as in the others, we have endeavored to apply tests as severe as could ever possibly be encountered in practice.
Fig. 1 (555). Apparatus for Trap Testing.
The apparatus used for making our tests is illustrated in the accompanying drawings.
Figure 1 represents a straight stack of 4" soil-pipe, such as is used in ordinary house-plumbing. The stack is built exactly perpendicular, and without bends from the outlet above the roof to the horizontal run under the basement floor, a distance of 70' 9". The soil-pipe was run up straight in this manner in order to furnish the conditions for the severest possible tests for siphonage and back-pressure. At the same time it forms the arrangement most commonly met with in practice, and the one most to be recommended. The unbroken fall of the water through such a pipe evidently creates the most powerful compression of the air in advance of it, and the greatest rarification behind it.
Just below the fourth floor is placed a large cistern, 44" long, 16" wide, 15" up to overflow, inside measure; or of 46 gallons capacity. The cistern served also to illustrate the action of a bath-tub, by having a 1½" discharge-pipe at its bottom trapped with a Bower's large size trap, and entering the soil-pipe just above the entrance of the water-closet waste.
The water-closet used was one of Zane's plunger water-closets, a kind well known, and widely used in this country. To expedite its filling a large service-pipe from the cistern was used, and the water was allowed to fill the cistern through a briss compression-cock. The water-closet is supplied with a regular overflow-pipe, so that, when full, its capacity is always the same. This capacity is a little over 4½ gallons in the closet used in these experiments.
To test the effect on traps below of emptying the tank after the manner of a flush-tank, a 4-inch outlet-valve and waste-pipe were fitted up in the manner shown.
Outlets were left on each story below the water-closet for testing the traps at various heights on the stack. The soil-pipe was ventilated at the top full-size, and had the usual foot-vent. This completes the apparatus for the experiments on siphonage and back-pressure.
For the experiments on evaporation a 4" galvanized-iron flue was erected by the side of the soil-pipe. This flue terminated just below the first floor in a galvanized-iron lantern, with a glass door on its front side. A 1½" rubber tube was connected with the bottom of the lantern, and an anemometer was placed above the point of connection in an enlargement made to receive it. The anemometer was so arranged and placed that it would measure accurately the current of air passing through the rubber tube in either direction. The galvanized-iron flue could be tested either cold, or heated by gas-jets as shown in the drawing. A second lantern was placed on the third floor, with a similar appliance for heating the flue.