We found that the discharge of either or both closets instantly broke the seal of an unvented S-trap whether the soil-pipe were the full length or shortened to half its length by opening the middle plug. When the falling water in the soil-pipe produces the partial vacuum behind it as it descends, if the soil-pipe extension above it is short and closed at its top, the action is at its maximum because there is very little air to expand. If the pipe is short and open at the top it is at its minimum. If it is long and closed still the action is powerful, but if it is long and open above, a medium effect is produced, and this was the condition we had in these tests.

With these great testing machines they showed the City Board of Health of Boston some exceedingly interesting experiments, which proved to that august body that their official ideas about plumbing fixtures were in many respects entirely wrong. The Boston Society of Architects came also to see these experiments, and, later, they were shown before the Suffolk District Medical Society of Massachusetts. The fame of these investigators extended soon to Europe; and an earnest request was made by eminent sanitarians in England to allow the result of these investigations to be published there in the interests of sanitary science. This important work of the laboratory has been under the direction of Mr. J. Pickering Putnam of Boston; and I am sure that his experiments and investigations are the most comprehensive and thorough and valuable that have ever been made on the subject of household sanitation." William E. Hoyt, C. E.. S. B.. Chief Engineer of the Buffalo, Rochester & Pittsburgh Railway Company, in an address on "Household Sanitation," delivered before the Rochester Academy of Sciences, Jan. 11, 1886.

We next ventilated our S-trap with a vent-pipe the full size of the bore of the trap. Leaving the soil and vent

Fig. 250. Apparatus for Trap Testing used at the Massachusetts

Fig. 250. Apparatus for Trap Testing used at the Massachusetts pipes full length, we found three discharges of the two closets was sufficient to destroy the seal. Thus we showed that with the long stack of pipe our ventilation signally failed. We next cut off half the bends and half the length of both soil and vent-pipe, leaving a medium length of each of forty-five feet of new pipe, and we found that four discharges of the two closets destroyed the seal.

Institute of Technology.

In the next experiment we broke the seal with two discharges using a 1-inch vent pipe, and afterwards broke it with four discharges on shortening the vent to 15 feet. This gave a shorter vent-pipe than we should ever be likely to encounter in practice. Hence if the friction produced in this short length of pipe is enough to prevent the effectiveness of the vent, anything longer than this would have destroyed it still easier. This shows that our expensive venting is utterly untrustworthy. In the Boston Board of Health tests the same results were obtained by the discharge of a single plunger closet.

The tests were made on a 2-inch by 4-inch Y. In our experiments for the City Board of Health we were severely criticized by "The Sanitary Engineer" for using a 4-inch by 4-inch Y branch, which we were told, would produce an action at least four times as powerful as the smaller branch. In order to test this point we connected our waste with the 4-inch by 4-inch branch shown immediately below the 4-inch by 2-inch branch and made preparation to repeat the last test under the new conditions. We cautioned the audience who were seated nearest the trap to hold firmly to their seats, which had been tightly screwed to the floor in order to prevent them from being sucked bodily into the drains by the prodigious siphoning power of the 4-inch by 4-inch branch claimed by "The Sanitary Engineer." On discharging the closets, however, we found no appreciable difference in the two Ys, and the gentlemen in the first row were then advised that they could confidently release their hold upon the furniture.

When the mouth of the vent-pipe has become partially closed by the gradual deposit of sediment, the supply of air through it is proportionally retarded, and it becomes less and less of a safeguard against siphonage. We had made a great many experiments in this field and found the resistance exactly proportioned to the size of the vent-pipe. The stack of pipes shown in Fig. 251 shows a trap vent pipe 125 feet long in a tall apartment house, which in compliance with the building law I was obliged to specify. As you see by the drawing the lavatories are placed over one another in such a position that the distance from their traps to the main ventilated soil pipe is not over 18 or 20 inches. These short branch wastes were powerfully flushed at each usage of the fixtures by a stream of water filling them "full bore," and discharging at the rate of nearly half a gallon a second. Traps were specified which cannot by any possibility be siphoned out, nor even have their seals seriously lowered. No better illustration of the wastefulness of this requirement could be found. The owner in this case lost over a thousand dollars for the privilege of seriously endangering through evaporation, the water seal of every trap which is not kept constantly in use throughout the hotel.

Fig. 251. Trap Vent Pipe 125 ft. long in a tall Apartment House.

Fig. 251. Trap Vent Pipe 125 ft. long in a tall Apartment House.

Trap Testing Apparatus 263

S-trap A had a vent as marked Vent No. 2; all Other traps were veutilated by the stop-cock attached to Y-branch B, where all traps were tested.