dip of a round-pipe trap, as fig. 83, or in the "Anti-D," fig. 81.

Although no water-leakage would be indicated by any number of defects in that part of a dip-pipe which stands within a trap, the bad air in the soil-pipe would find an easy passage to the house side of the water-seal of the trap through only a small defect, as shown by the arrows in fig. 73.

12. At the discussion which followed my lectures ten years ago, an "improved " D-trap was talked about, a trap which had no existence prior to my criticism of the D-trap in general use. But, as I have explained elsewhere, this

Fig. 75.-VIEW OF THE "NARROW-
BAND" D-TRAP, WITH SQUARE
PIPE OUTLET (J).

trap possesses all the great evils of the old trap. The improvement consists in bringing the two cheeks (the sides) of the trap closer together, so as to leave as little space as possible between the dip-pipe and the inner sides of the cheeks, as shown on plan, fig. 74, i.e., in the fullsized D-trap, the band, c, fig. 72, is 6 in. wide, but in this trap, figs. 74 and 75, it is only 4 in. wide, so that the cheeks of the trap stand closer together by 1 in., making the trap more compact, and less difficult to flush out. But to call this trap self-cleansing would be misleading, for the inner surfaces of the trap are just the same as in the fullsized D-trap, minus about 5 in. sup., for the narrower band and narrower top, i.e., the internal surface of this " narrow

band" D-trap would be equal to about 3 ft. sup. No scouring flush could be sent up the two vertical angles, a and B, fig. 74, nor at D and c, so that these parts would become lodgments for filth; and the dip-pipe, though it would often get splashed over with excremental matter, would rarely, if ever, get thoroughly cleansed, for no frictional force could be brought to bear upon it, from F G H, and upwards. Then there is the evil of the dip-pipe being inside the walls of the trap (Art. 11).

13. The criticisms on the usual form of D-trap brought the "Helmet" D-trap into notice, but a moment's examination of the trap, illustrated in fig. 76, will suffice to show, that whilst the lower part of the trap is improved,

Fig. 76.-VIEW OF THE "HELMET" TRAP.

all the bad principles of its elder brother are retained. As a matter of fact, nearly a quarter of a century ago I had our D-traps made up in a similar fashion, except that instead of burning the edges of the lead together, they were soldered. The lower part of the trap, the body, was bossed up on a hardwood

block, in shape as shown in fig. 76.

14. In Table No. 1, in the following chapter, the results of several tests made with both "non-cleansing" and self-cleansing closet-traps are given, to show at a glance the difference in the number of clean-water flushes required to rid the various traps of certain matters put into them. And as a practical proof was given to the audience, in one of my lectures in the rooms of the Society of Arts, of the difficulty of freeing even a small-size D-trap from filth, when once it had become fouled, an illustration of the trap used is given on the next page; and an extract from the "Lectures" is also made, as the result of the experiments may not be without interest to the student plumber.

"I will not say any more on the D-trap for waterclosets; and instead of occupying your time with a lengthy criticism on the smaller sizes for trapping off what are called 'dirty water' wastes (to distinguish them from sewage wastes, soil-pipes, drains, etc.), we will give a few practical experiments to show their unfitness for such purposes. In doing this, we will not aggravate the case by using the trap unfairly, for instead of using such adhesive matter as greasy water from saucepans, etc., we will use a little soapy water, and after

that some plain water with a little stone-blue put into it to colour it.

size

A

|= IFT

SCALE IN=

Fig. 77.-SMALL-SIZE D-TRAP,
WITH GLASS CHEEKS.

"I have had a small-size D-trap made with glass cheeks to it, for you to see the working inside, and this trap is connected to a small wash-hand-basin with 1 in. brass plug-andwasher, the usual being only in. This trap is made much smaller than the usual'small-size' handmade D-trap, or than the small-size cast-lead D-trap, so that any experiment made upon it will be more favourable for cleansing it than would be the case with the D-traps as generally used in practice." Fig. 77 illustrates this trap, B, with a small wash-hand-basin, A, fixed upon it. The depth from the top to the band is 4 in., the width of the band, between the cheeks, 3 in., and the length along the top 6 in. The dip-pipe first used was 1 in., and the distance from the bottom of the basin to the standing water of the trap is 8 in. The short length of waste-pipe, c, consisted

of a piece of glass tubing. [In some subsequent experiments the dip-pipe was increased in size to 1 in., with a similar result, a non-cleansing of the trap.]

"Two or three experiments were then made with this model, to show the non-cleansing nature of D-traps. Some blue water, i.e., water coloured with stone-blue, was put into the trap, and though two or three charges of clean water from the basin were sent into it, the whole of the blue water was not removed. The trap was then charged with soapy water, as in practice when fixed under lavatories would be the case, but though several flushes of clean water from the basin were sent into the trap, every vestige of soapy water was not removed, and with one

flush the suds remained strongly in the trap, floating about and around the dippipe.

"The experiments showed clearly enough how such traps become cessAnd yet

Fig. 78.-SECTION OF pools, or filth-collecting boxes.

there are thousands of such traps in use in England to-day, under baths, sinks, urinals, safes, lavatories, and water-closets."

15. The bell-trap is only introduced here to show the student plumber how poor a trap sufficed to satisfy the ideas of plumbers of a past generation; for to-day no plumber with any sanitary notions would venture to palm off so inadequate an appliance for preventing the passage of bad air into a house.

Its depth of water-seal is so small that the banging to of the door of the room where it is fixed, with the windows shut, would almost suffice to break the seal; but apart from the effect of any concussion of air upon the seal, it would soon be diminished by evaporation, or by capillary attraction from a piece of rag, hair, cotton, or worsted hanging over the weir of the trap, at c. Nor is its apti

tude to lose its water-seal the only grievance caused by it; for to the cook, housemaid, and scullery-maid the great grievance is that they have to waste so much time in getting their slops through it.

16. As all mechanical appliances get out of order sooner or later, and as traps with mechanical seals, or check valves, have such devices fixed inside them where they cannot be seen, it is better not to trust to them, but to fix traps which have no parts or appliances to get out of order-traps which, with an anti-syphoning pipe, may be trusted to last as long as the fixture under which they are fixed, so that the failure first of that part which is visible shall lead to an examination of that part which, in the case of certain fixtures, is always out of sight. I have treated this subject more fully in "Dulce Domum."

T

CHAPTER XXI.

SELF-CLEANSING PLUMBERS' TRAPS.

1.

O examine and criticise the various traps fixed by plumbers throughout the United Kingdom would need more space than is contained between the covers of this book; but having in the previous chapter discussed at some length the non-cleansing class, the traps which, like ponds, are filth-accumulators; and the traps which, when defective in certain of their parts, to the eye, even on close examination, would show no defect; as well as that most illusory of traps, the bell-trap; it will not occupy much space to discuss the self-cleansing class, the traps