WATER seal traps bear the same relation to mechanical traps that the hopper water-closet bears to pan, valve and plunger closets. They accomplish their work of removing the wastes and excluding sewer gas much more perfectly by the simple action of the flushing stream, and by the water seal which it forms, than do the complicated machines already described, and they must be placed far ahead of them. Here again the leading sanitarians are in accord; but as is the case with hopper closets, so it is with water seal traps, there is the greatest difference in the manner in which the different kinds perform their duties.

Our first general division of water seal traps is into (a) Sediment or Cesspool Traps, and (b) Self-Cleansing Traps.

(a) Sediment Traps. - Sediment traps may be designated as those whose inner surfaces are not cleaned by the scour of the water passing through them, but which gradually become coated with a deposit of filth. The deposit is due to the improper form and size of the water passages, which sometimes cause the current to pass through them sluggishly and without exerting upon them sufficient friction to keep them clean, and sometimes furnish chambers or pockets in which no movement at all takes place.

We have subdivided sediment traps into (1) Air-Vent Traps, and (2) Reservoir Traps.

Fig. 90. Common  Pot.  Round or Cesspool Trap.

Fig. 90. Common "Pot." "Round" or "Cesspool" Trap.

(1) Air-Vent Traps. Fig. 91 represents a trap having an air valve. The exclusion of soil-pipe air, therefore, depends entirely upon the accuracy of the fit of this valve alone, without the aid of water. We have already explained that such a valve could never be made gas tight, even when new, where its weight is expected, as here it must be, to perform its purpose of protecting the water seal below from siphonage. Such an air valve, if applied at all, should be placed above the trap far enough from the waste water to be beyond the reach of contamination therefrom. As here placed, the hinge would quickly become corroded enough to deprive it of the sensitiveness of action necessary to prevent the destruction of the light body of water in the trap by siphon-age. Nevertheless, the idea underlying this trap is good; namely, to apply a very small air valve far enough above the trap seal to be entirely out of the way of water spattering and sufficiently sensitive to supply air to the waste pipe before siphoning action can overcome the feeble inertia of the water seal. It is the principle of the Morey and McLellen vents.

Fig. 91. Air Vent Trap.

Fig. 91. Air Vent Trap.

Fig. 91b. Morey's Air Vent.

Fig. 91b. Morey's Air Vent.

(2) Reservoir Traps.

Figs. 90 to 105, inclusive, represent various forms of sediment collecting traps. The most famous in this country is the pot trap (initial cut), Fig. 90. The unfortunate D trap, common in England, is shown in Figs. 92 to 98. This D trap is as much despised here in America as our favorite pot trap is in England. It is difficult Jo account for the national fondness for either of these abominations, now very cheaply made by machinery, after so much better de-

Fig. 91c.

Fig. 91c.

Fig. Old

Fig. Old vices have been furnished. But both forms, as well as the globe trap (Fig. 100) and bottle trap (Fig. 91) are hard to siphon when the size of the body is made large enough in proportion to that of the inlet and outlet pipes, and this fact, together with the ease with which they could be manufactured by hand on rainy days, has made them favorites, in spite of the absence of all science in their form and construction .

Water Seal Traps 104

Fig. 92.

Water Seal Traps 105

Fig. 93.

Water Seal Traps 106

Fig. 94.

Water Seal Traps 107

Fig. 95.

Water Seal Traps 108

Fig. 96.

Water Seal Traps 109

Fig. 97.

Water Seal Traps 110

Fig. 98

Water Seal Traps 111

Fig. 99

Water Seal Traps 112

Fig. 100.

Water Seal Traps 113

Fig. 101.

Fig. 101a.

Fig. 101a.

Although the pot trap is liable to collect sediment and become at times very foul within the cesspool chamber, it may, nevertheless, be made antisiphonic, and, if the walls are sound, the foul gases within it cannot escape into the house under normal conditions. All they can do is to remain in the trap until they are driven out by the next current of water that passes through it; only with unventilated soil pipes do these cesspools become a source of serious trouble. Yet if a choice had to be made between the evils of an unventilated pot trap and a ventilated siphon trap there should be no hesitation in preferring the former.

The bottle trap (Figs. 91 and 100) are equally good with the floating ball trap of equal size in resisting siphonage and in every other respect, and they are much to be preferred to it, inasmuch as they are not encumbered with any mechanical part.

Fig. 91 bis shows an inverted bottle trap, the interior pipe becoming the outlet instead of the inlet. In this case, the outlet pipe is sometimes flared out, trumpet shaped at the end. This may somewhat increase its resistance to siphon-age, but it also evidently tends to obstruct the water flow, and forms a nucleus for the collection of sediment, hairs, lint, etc. A better way to increase the antisiphon feature is to increase the diameter, if a bottle trap is to be used at all.

Fig. 62 is an old form of D trap called the "Goose" trap, a cesspool trap of rarely appropriate name.

Figs. 94 to 99 represent some cesspool traps at the Museum of Hygiene at Washington, and described by Mr. Glenn Brown, architect, some of them having been presented by Mr. S. Stevens Hellyer of London. They show the heavy deposits formed in these unflushed cesspools and the chemical action on their metal work, especially where soil pipes are unventilated under abnormal conditions.

In the first figure, which is a water-closet trap, the inlet pipe is almost closed by deposits, and the waste pipe entrance (A) from another fixture is completely closed up.

Fig. 97 shows a piece sawed off from the bottom of a D trap. Over a third of the entire area of the trap seems to have been taken up with the deposit.

Fig. 98 is a section of a lead D trap having an incrustation below the water line averaging over an inch in thickness. Two waste pipes entering below the water line were nearly closed by deposits, the waterway remaining in them being not over 3/8 inch in diameter. The analysis of the incrustation in this trap showed calcic phosphate, 37.I2 per cent; plumbic phosphate, 1.45 per cent; calcic carbonate, 32.11 per cent; volatile and organic matter, 17.82 per cent, and water, 11.50 per cent.

Figs. 95 and 99 show waste pipes completely closed in traps which had been in postion forty-five or fifty years.

Fig. 101 is a pot trap having its inlet and outlet pipe connections arranged in such a manner as to improve the scouring action of the water passing through it. But a fixture having its outlet large enough to fill the waste pipe "full bore" and constructed so as to be discharged "full bore," must be used with such traps, as indeed with all traps, if the cleansing power of the flush is to be of any service.

Figs. 102 and 103 show a bathtub trap.* Its purpose is to permit of cleansing it from the floor level. Made of sufficient diameter it would easily resist siphonage and is very convenient where it is necessary to sink the body of a trap between floor joists. Figs. 104 and 105 show ordinary pot traps in the same position.

•Made by the Webb Manufacturing Co. of Boston.

Water Seal Traps 115

Fig. 102.

Water Seal Traps 116

Fig. 103.

Water Seal Traps 117

Fig. 104.

Water Seal Traps 118

Fig. 105