No. 151. Development of Pattern for Tapering Sleeve for Vent on a Flat Roof.

Trap Ventilation. Needless multiplication of soil and vent connections is undesirable, but certain principles must be carried out to secure aperfect job. These have often been curtailed by the extremists of one class, and at expense of the quality of work. It is the extremists who regulate progress and keep things at a reasonable mean. The extremists in progression would drag us into practices perhaps unsafe; while their opposites, derisively termed "old fogies," hold us back, sometimes on untenable ground. The result is that the conservative element is the safest class to follow; it neither discards a well-tried method nor embraces a new one, without good reason to sustain the action. As before intimated, the change in character of buildings and mode of life has necessitated a maze of pipe work in some buildings, which to the uninitiated looks like a senseless network thrust on the owner to the pecuniary gain of the plumber. This is not the case, as every plumber well knows; and he can easily disarm this type of creduality by being well versed in the philosophy of his business. The familiar cry that crown ventilation* of traps destroys the seal by evaporation, is often but the echo of the voice of a man with an axe to grind. The deep-seal trap costs but a trifle more than the ordinary. There are also positive mechanical means - comparatively cheap, too - of protecting a vacant or unoccupied house against sewer air. In occupied houses, there is no chance for traps to lose the seal by evaporation; and, when properly piped, the evaporation of seals does not take place so fast as might be supposed. The crown vent is merely, or should be, to keep the water from being siphoned out of the trap. It is the practice of making the crown vent do duty not only as a siphon-preventer but also in the capacity of a stack vent, that has created the impression as to rapid evaporation.

No. 152. Elevation of Tapering Pipe-Sleeve for Pitched Roof.

Fig. 153. Common Form of Crown and Stack Ventilation..

* There is an increasing disposition to substitute continuous ventilation for crown ventilation.

If we bring a branch waste to a fixture just as though it was to be a "dead-end" connection, and then put in a liberal crown vent continued to the roof, as shown in Fig. 153, we have filled the letter of most specifications, because we then have crown ventilation and stack ventilation. But this is not the spirit of the work specified, nor is it up to the standard of intelligent workmanship. The current to the roof passes up the trap leg, and thence-through the crown vent directly to the open, being brought on its way in close proximity to the seal of the trap; and it is no cause for wonder that such a connection would rob an ordinary trap of its seal within a surprisingly short time, if the fixture is left unused. This is the type of installation found in the wake of speculative builders, scrimping plumbing contractors, and ignorant or unscrupulous journeymen. Many examples of this double-duty vent pipe are seen, in which the workman foresaw the result to some extent, and, in attempting to counteract the supposed ills of evaporation, made the vent useless as a siphon-preventer by connecting the vent 10 inches or more below the crown of the trap, as shown in Fig 154. The proper way is to make both the waste and the crown vent branches from other lines. Of course, if it- is the top fixture, or there is only one on the line, the waste stack may end in the beginning of the vent stack or connect into the vent stack, as in Fig. 155, according to circumstances. The main current goes by the most direct route - up the main waste and vent stacks of the string. If the crown vent and waste stacks stand close together, as in Fig. 156, we have the loop effect before spoken of; and with the fixtures near the stacks, the waste and crown-vent connections are both short - which is proper. It is poor practice to have the stacks far away from the fixtures, because one is then likely to fall into the error of allowing the crown vent to act also as a direct line vent for the branch waste. This plan is such a short-cut to accomplishing the work of roughing-in, that the temptation to err is great. If the waste stack cannot come near the fixture, then follow the loop principle, and turn up and into the vent stack, branching the trap into the waste branch, and taking the crown vent into the vent stack, as shown in Fig. 157, or into a vent continuation of the branch waste, as preferred. If neither main stack can come near the fixtures, then loop out from the soil or waste stack to the fixture, and back into the main vent, leaving enough upright when Waste Stack is not pipe at the fixture end of each loop to branch the waste and crown vent into, as illustrated in Fig. 158. In this way, half of the branch loop acts as a waste, and half as a vent, and there is ventilation through the soil or waste branch part without continually pulling the air into juxtaposition with the trap seal. Also, the local branch waste to the trap and the crown vent pipe are thus permitted to be as short as desired.

Fig. 154. Prevention of Siphoning Thwarted by Improper Placing of Vent Connection..

Fig. 155. Waste Stack Connected to Vent Stack above High est Fixture..