THE young plumber having in the days of his apprenticeship or mateship and improvership acquired the knowledge of joint-making and pipe-bending, is then in a position to assist in the execution of the internal plumbers' work of a building; but as the first thing generally to be done is to fix the soil-pipes, the traps for the closets must first be determined upon.

2. In the evil days, when traps for the closets, sinks, baths, urinals, and lavatories were made up by hand, according to the sweet will of the plumber, he generally so willed it that they should be of the most accumulative kind; and so to every appliance, sanitary or otherwise, requiring a trap, he fixed an unsanitary D-trap.

3. In limiting the size of a trap to 9 in. or 10 in. the maker of the trap was not so much governed by the depth of his wisdom as by the depth of the joists - the space between the closet floor and the ceiling; as in scores of cases on ground floors, where there was no such limit, 13 in. and even 16 in. traps have been found fixed under pan-closets, the nature of which would tend to increase rather than to diminish the evil of so large and so foul a trap. I have seen a lead trap of the D-trap kind with two dip-pipes into it, and two pan-closets fixed upon it. The size chiefly used for fixing under a wash-hand basin was 6 in., no matter how small the basin or little its waste-plug; and it is not at all an infrequent thing, in making an examination of the sanitary appliances of a house, to come across 7 in. and even 8 in. D-traps fixed under small lead-lined sinks, with a round-hole waste-grating only equal to the flushing-out of a 1 1/4 in. round-pipe trap.

4. From the many old D-traps which have been cut out in the last twenty years, it may fairly be said that the greater the capacity of the trap the smaller must have been the capacity of the man who made it.; for whilst a man here and there did his utmost to improve it by contracting it, notwithstanding the size of the dip-pipe,4 1/2| in., and the size of the soil-pipe from it, 4 1/2 in. and 5 in., the generality of men, when they found they could not make a trap of the depth they preferred, increased its width to make up for it, whence traps with 7 in., and in some cases even 9 in. bands. A pailful of filth has been taken out of many such a trap.

5. It may seem curious to search for any reason in the maker of a large D-trap, yet he had reasons for making his traps deep and wide. In the larger size for closets - the 10 in. instead of the 9 in. - he could not only put the dip-pipe further down into the trap, to give it a greater depth of seal, but he could also increase the size of the hole to the outgo, making it round instead of A -shape. And the wider band - 7 in. and 9 in., instead of 6 in. - gave him a wider base upon which he could the better solder the end of the soil-pipe, which was often 5 in. bore.

6. In the case of D-traps under sinks and lavatories, experience taught the plumber that such traps soon stopped up; but rather than abandon that type of trap for one of a " self-cleansing" kind, he preferred to increase the size of the trap, so he made it large enough to solder a 4 in. or a 4 1/2 in., and in some cases even a 6 in. brass cap-and-screw in one of its cheeks, for a man's hand to be put into the trap, to remove any obstruction, and to clean out the accumulated filth. In examining a Fire Insurance Office in the city of London only a few months ago, it was found that a 12 in. D-trap with a 9 in. band, a 6 in. outgo, and a 5 in. brass cap-and-screw, had been fixed, within the last few years, under a lead-lined sink, the discharges from which would only be equal to filling a pipe l 1/4 in. bore.

7. The D-trap has had a long reign in England, from the days of the privy, a century ago, to the dawn of house sanitary science, within the last two decades, when it was dethroned; although to this day it is not without its advocates, and a benighted man here and there about the country, and especially in London, still goes on fixing them, disgracing the craft with his evil practices. A few technological students, unlike Caesar's wife, are not without suspicion; but judging from their written papers a very large majority of the students have a good knowledge of traps, which must be very gratifying to their teachers. If what has been said already and what follows does not convince the sceptic - the maker of D-traps - of the error of his ways, neither would he be convinced though one of his victims returned to upbraid him.

8. About the first form of trap used for fixing under water-closets was the syphon trap, i.e., a pipe bent and recurved in the shape of the letter S; but as the water in such a trap was easily syphoned or momenturned out, and the means of preventing such a loss of zeal little understood, the D-trap was invented. That the syphon or round-pipe trap was in use more than a century ago is proved by the date of Cumming's patent, where, in 1775, he shows a syphon-trap under a valve-closet, fig. 121, Chap. XXVIII.

9. There is proof in the records of the Patent Office that the D-trap was in use in 1790. Fig. 70 represents perhaps the oldest form of it, with its cheeks soldered outside to the band; by this method the cheeks could be kept closer together than when the cheeks were soldered to the band inside the trap, and still give a wider base for soldering the outgo - the soil-pipe - to the trap.

Fig. 70. - View of a D-Trap, Early Shape.

Fig. 71. - View of a D-Trap, Modern Shape.

10. The internal surface of a 9 in. D-trap, fig. 71, is nearly double that of a 4 in. round-pipe trap, fig. 83; and even the improved D-trap - the 4 in. band trap - is twice that of my "Anti-D," fig. 81, though a body of water can be discharged in less time through the "Anti-D" than through the D-trap. The internal surface of a 9 in. D-trap with a 6 in. band is about 3 ft. 6 in. sup.; in the " improved " or narrow-band D-trap it is about 3 ft. In a 4 in. round-pipe trap, as fig. 83, it is under 2 ft.; in my closet "Anti-D-trap," fig. 81, it is only about 15 or 16 in. The outgo is not considered in the measurements of any of these traps.