Fig. 246. 2 in. Pot.

Fig. 246. 2 in. Pot.

Fig. 247. 2 in. Pot.

Fig. 247. 2 in. Pot.

Fig. 248. 3 in. Pot.

Fig. 248. 3 in. Pot.

Fig. 249. 8 in. Pot.

Fig. 249. 8 in. Pot.

Tests for Siphonage on Traps of Different Sizes.

The tests for siphonage were made on pot traps unventi-lated and on ventilated S-traps, the traps being placed on the Y branch outlet on the second floor at a distance of about II feet below the bottom of the water-closet trap, since at this point the siphonage proved to be most severe.

The tests were made with the closet alone, and also with the closet and bath-tub combined.

The result of the experiments was that the discharge of the water-closet was sufficient to unseal the S-trap even though it was ventilated at or below the crown in the manner prescribed by the plumbing regulations with vent pipes of the full size of the trap. It made no material difference as to siphonage whether the vent-pipe be applied immediately at the crown or at a considerable distance below it. Had the pipes been partially clogged by sediment or rust the results would, of course, have been even more serious.

An unventilated S-trap was, of course, completely siphoned out by a single discharge of the closet, leaving only a few drops of water in the bottom of the bend.

A 1-inch S-trap having a 1- inch vent hole in the crown and a 1-inch pipe of smooth clean lead 17 feet long attached to the opening, had its seal broken in three discharges.

A 1-inch S-trap with 1-inch vent, constructed as shown in the slide, and having 7 feet of 1-inch pipe attached to one of the vent openings, the others being closed, lost its seal after 5 discharges. With a 17-foot vent-pipe 4 discharges sufficed. When the bath-tub discharge was added to that of the water closet a single discharge broke the seal with the 17-foot vent-pipe and swept nearly all the water out of the trap.

Experiments on the Pot Traps.

The pot traps tested on these occasions measured respectively 2 inches, 2 inches, 3 inches, 3 inches, 4 inches, 5 inches, 6 inches and 8 inches in diameter, and from these tests we found that their power of resistance to siphoning depends upon their size, and more particularly upon the diameter of the body, a half-inch excess of diameter affording a very considerable excess in depth of seal. With equal depth the resistance will be in direct proportion to the diameter. The 2-inch pot lost its seal in one discharge of the water closet, a 2-inch pot in two discharges, a 3-inch in four discharges, a 3-inch in seven discharges, a 4-inch in seven discharges, a 5-inch in 22 discharges, a 6-inch in 27 discharges and an 8-inch lost 1 inches of its seal in 24 discharges, and would probably have resisted for several hundred discharges. In well arranged plumbing, however, a pot trap having a body 8 inches in diameter and having 1-inch or 1-inch connections, may be considered perfectly safe so far as retaining its seal is concerned, so long as its seal is not contracted by deposits.

An examination of the sectional drawings of all the traps will show at a glance the effect of each discharge on its water seal, the horizontal lines giving the exact level of the water after each discharge.

The next figure (250) shows the apparatus erected at the Massachusetts Institute of Technology already referred to.* It consisted of a stack of four-inch soil-pipe with two water-closets set ten feet above the wastes of the traps to be tested. The closets were a Zane and a Jennings, both quite popular at the time these experiments were made. The soil-pipe had a number of bends to exemplify the bends, more or less of which are usually required in any tall building. The vent-pipes are on the right and were of 2-inch cast iron pipe, also with bends. Openings were left in both stacks of pipe, as shown in the drawing, to permit of a great variety of experiments with long and short piping, and with from only 1 up to 8 on the soil-pipe stack, and from 1 to 13 on the trap-vent stack.

*Mr. Wm. E. Hoyt, C. E., writes of these tests as follows: "A few weeks ago I visited a mechanical laboratory, where, for over two years, a series of experiments has been conducted on household sanitation. Neither time nor money has been spared to make these experiments and investigations thorough and complete. Here, several skilful sanitarians have been diligently at work in all this time to improve our system of house drainage. One of these men is well known in Europe, as wen as this country, by his scientific investigations and his writings. Let us see what they have been doing. Time will allow a reference to one or two things only.

"These men wished to know just how traps and ventilation pipes and other contrivances really worked, under all possible conditions, in houses fitted with modern appliances, and to ascertain this, they bought a lot of full sized drain-pipes and ventilation-pipes and traps and water closets, and set them up in their laboratory just in the way they are put into our houses. except that they econo-mized space, as I shall show you by a drawing. (Diagram C.) Fig. 250.

In this way the apparatus was made to correspond with that in any form of house we desire to imitate. Some of the tests were very severe, but no more so than often encountered in plumbing practice. If we are to be forced by the law to put our clients to the great expense and danger of ventilating every trap, we have the right to demand, first, that the means employed shall actually afford us the security it, pretends to, and not fail at the first critical moment; and second, that no other simpler and better means exist for securing the desired result.