(4) The following is the water capacity of the traps tested.
The 8" pot-trap holds 5 quarts or 10 pints.
The 6" pot-trap holds 3 quarts or 6 pints.
The 5" pot-trap holds 2½ quarts or 5 pints.
The 4" pot-trap holds 2¾ pints.
The 3½" pot-trap holds 2½ pints.
The 3" pot-trap holds 2 pints.
The 2½" pot-trap holds 1¼ pints.
The 2" pot-trap holds ¾ pint.
The 1½" S-trap, with 5" seal, holds ¾ pints.
The 1½" S-trap, with 1¾" seal, holds 3/8 + pints.
The 1¼" S-trap, with 1¾" seal, holds ¼ - pints.
The "Sanitas" holds 1½ pints.
A piece of 1½" waste-pipe 12" long holds about ¾ of a pint of water. A similar piece 15" long holds a pint. Hence a trap used with such a waste-pipe should have a capacity of not less than ¾ pint. Accordingly, all unventilated1¼" S-traps and all unventilated 1½" S-traps having less than 5" seal are incapable of resisting the back-pressure liable to be encountered in plumbing.
III. Experiments on Evaporation Produced by Trap-Ventilation.
These experiments were made in the basement floor, as already explained.
They may be subdivided into (A) those in which the vent-pipe was conducted into a cold flue, and (B) those in which the vent-pipe was conducted into a heated flue.
(A) Experiments on Evaporation Produced by a Cold Ventilating Flue.
(a) 1¼" (scant) S-trap having a seal of 4 5/8" deep was attached to the end of the branch waste in the manner shown in Fig. I. A 1½" rubber ventilating pipe was taken from the 1¼" ventilating opening at the crown of the trap, and conducted into a cold 4" galvanized iron ventilating flue, shown in the drawing. This flue passed through two occupied offices (basement and first floor) whose temperature was maintained at about 68° Fahrenheit, during the term of the experiments, and through a chemical laboratory (second floor) whose temperature was maintained at about 6o°
Fig. 28 (582)
Figs. 30 (584)
Fahrenheit. For the remainder of its height the flue passed through a cellar and stairways, whose temperature was maintained at about 45° Fahrenheit. No artificial heat was applied to the flue.
The velocity of the movement of the current of air in the flue was measured by the anemometer. The daily rate of loss of seal by evaporation, and the velocity of the current in feet per minute is shown in actual size by the accompanying diagram, Fig. 27* to 29.
We see that the loss averages about an eighth of an inch per diem. It amounts to about a quarter of an inch the first day, and gradually diminishes as the level of the water descends in the trap, and the distance of its surface from the ventilating current increases, to a little less than an eighth of an inch per diem. Hence an ordinary S-trap having a 1½" or a 1¾" seal would lose its seal in from nine to eleven days.
(b) The experiment was repeated several times at different parts of the year, from the middle of December to the middle of May, with substantially the same results. Fig. 29 represents the record of a second of these experiments.
(c) The same trap was now vented at the middle opening, whose center was 2" below the center of the upper opening. The rate of evaporation was somewhat slower, as shown by diagram, Fig. 28. This experiment was carried on only eleven days, inasmuch as by this time 1½" of the seal had been destroyed, and the seal of ordinary machine-made S-traps does not exceed 1½" or 1¾".
(d) The same trap was now ventilated at the lowest point, i. e., 6" below the crown. The evaporation in this case was exceedingly slow and after the first two or three days was almost inappreciable.
*These outs have since been reduced to about 1-2 their original dimensions, so that they are now about on-half full size.
(e) A number of experiments were then made on S-traps unventilated but open in both ends as is the case in practice. The loss of water was almost inappreciable, not exceeding 1/32 or 1/16 of an inch in ten days.
(B) Experiments on Evaporation Produced by a Heated Ventilating Flue.
(a) A 1½" trap having a seal 3¼" was tested. A 1½" wrought iron gas pipe 6" long connected the crown of the trap with a brick flue 8"x 12", heated by a stove. See Fig. 1.
Diagrams, Figs. 30, 31, 32, 33 and 34, represent five tests, two made in March, one in October and two in November of 1883. Here again the perpendicular lines represent, in actual length, the depth of seal of the trap. The upper arc represents conventionally the outlet mouth, and the lower arc the inlet mouth of the trap. The horizontal lines show the position of the water level in the trap at the same hour in the morning of each day recorded in figures on the diagram.