Fig. 173.

Experiments On Siphonage Severest Strain 186

Fig. 174.

Experiments On Siphonage Severest Strain 187

Fig. 175.

Experiments On Siphonage Severest Strain 188

Fig. 177.

Figs. 164 to 177 inclusive. Horizontal Traps with Combined Curved and Straight Partitions.

We have found that these defects can be obviated by taking advantage of the principle of centrifugal force. Accordingly we constructed the partition in the form of a spiral as shown in Figs. 178 and 179.

This improvement constitutes our third step, and in it we have attained a form which combines the advantages of all the preceding ones and eliminates completely their defects. We can reduce the horizontal dimensions as much as be-

Experiments On Siphonage Severest Strain 189Figs. 178 and 179.

Figs. 178 and 179.

Third Step. Plan and section of Horizontal Trap with Spiral fore without destroying the power of the trap to withstand the severest tests of siphonage.

Partitions.

We have done away with the comparatively clumsy method of using abrupt turns and baffle walls to separate the air from the water when siphoning action takes place, and have substituted for it the simpler and more scientific and effective agency of centrifugal force.

Air under powerful siphonage rushes through the trap with tremendous speed, causing some of the water in the reservoir to whirl around with the air like a miniature whirlpool and cyclone. The water, being the heavier of the two elements, is thrown outwards by its spiral movement against the outer walls of the partition, while the air hugs the inner walls because along them lies the quickest and easiest outlet to the drain pipe where the partial vacuum to be filled by it exists.

This action of the two fluids is easily followed by the eye if the upper side of the experimental traps be made of glass. It is made still more plainly discernible if lumps of earth, small stones and other substances a little heavier than water be mixed with it. These are clearly seen to hug the outer walls as they whirl around on their way to the outlet, while the air bubbles, always present in the water at the time of siphoning action, seek the inner side or more direct passage outwards, which is for them the line of least resistance.

The resisting power of this trap is, as shown by the table, as great as that of any of the preceding traps, while its form permits of a much more rapid discharge than the others in proportion to the length of its waterway, and it has the maximum of scouring action, and absolutely no obstruction or baffle in any way of the water discharges at any point beyond what is encountered in a perfectly straight smooth pipe. It has a sufficient volume of water to withstand back pressure and evaporation, and the distance between the trap proper and the drain outlet is sufficient to obviate capillary action.

I believe, therefore, that in this we have attained the principle of the perfect anti-siphon plumbers' trap.

Examined for friction, or self scouring properties, these spiral traps showed themselves, as might be expected, far superior to the others, as indicated by the friction tests recorded in Table III.

Table III. Experiments on Water Scour

Showing Time in Seconds Required for Water in Cistern Shown in Fig. 241 to Pass Through Traps.

Number of tests.

Traps tested.

1st Test.

2d Test.

3d Test.

Sec.

Sec.

Sec.

4-in. Pot Trap, 3 1-2-in. Seal.............

25

24

25

Straight Pipe.........................

22

22

22

7 1-2-in. Pot, 4-in. Seal......................

32

32

32

13-in. Sq. Trap, Fig. 138.....................

21

21

21

13-in. Sq. Trap, Fig. 141......................

35

35

34

13-in. Sq. Trap, Fig. 147......

55

55

....

13-in. Spiral, Fig. 178........

27

27

27

11-in. Spiral, Fig. 181........

32

32

32

11-in. Spiral, Fig. 180........

32

32

32

11-in. Spiral, Fig. 182........

28

28

7-in. Spiral, Fig. 185....................................

30

30

29

The 13-inch spiral trap, tested on the apparatus shown in Fig. 190, discharged the 12 gallons of water from the tub in less than half the time required by the rectangular trap of Fig. 147, 27 seconds being required for the former and 55 seconds for the latter. The tank holding 12 gallons, the first discharged about two quarts per second, and the second less than one quart. Moreover, it required from 5 to 10 seconds for pieces of paper, small lumps of earth and other articles thrown into the water to pass through the rectangular trap, whereas these matters were whirled through the spiral trap in less than half the time. Heavy substances, like small lumps of iron and lead, were retained in the rectangular traps, but were always easily and quickly whisked through the spiral trap and carried over into the waste pipe.

Now the scour exerted by the water in passing through the reservoir chamber of the spiral trap was found to be as effective upon the walls of the chamber as upon the dip of the trap proper, because it is in the dip of a trap that heavy matters are most likely to be caught and retained, not only because the bend is most sudden at this point, but also because these matters have here to be elevated by the amount of the depth of the seal, while in the reservoir chamber they have only to be pushed along a smooth horizontal surface.

When the waste outlet of a plumbing fixture is very much smaller than the area of the waste pipe connected with it, the water loses its scouring force and greasy matters will gradually accumulate along the walls not only of traps but even of the straight waste pipes themselves, as has been explained and illustrated in a previous chapter. Now our spiral trap is evidently no more able to resist the fouling effect resulting from improperly constructed fixtures than would be the straight waste pipe itself. But it has this all important advantage over a vented S trap, that whereas in the latter the vent pipe opening being the first part to be clogged by greasy deposits, the whole trapping system becomes at once destroyed, and this without any warning to the user; with the former the sediment being equally distributed over the inlet pipe and body of the trap, this reduction of the area of the waterway cannot in any way reduce the antisiphonic character of the trap, because it simply converts it into a smaller trap, having the same relative properties and principle of action. Indeed the sediment will tend to accumulate where the resistance to the scour is greatest, which is at the dip, and in this case the area of the trap proper will constantly diminish with relation to that of the reservoir chamber, in which event the resistance to siphonage will if anything tend to increase rather than diminish.