Q. I would like to have a few questions answered on the following plan. It is proposed to build a new wing to the county jail here, and according to the plans there are no traps on any of the hoppers, nor is there any vent-pipe from the top of soil-pipe, where the upper hoppers connect. There is to be one vent-pipe at back of building, where the rain-water pipe acts as another. Then in the front there is a 20-inch cast-iron smoke-stack, and on the inside of that is an 8-inch cast-iron pipe for vent-pipe. Now, I would like to know if the 3-inch outlet from the hoppers is not too small; also, if they should not be properly trapped? Or does the vent-pipe that goes up inside the smoke-stack take all the foul air down and up it, without letting any smell back in the cells? I wrote to the architect in Baltimore, and he says that they are not to have any traps, and that the 3-inch soil-pipe from hoppers to the large pipe is large enough. I contend that it ought to be 4-inch, and that all the hoppers ought to be trapped; and I also think that the pipe ought to continue up through the roof.

A. The system of drain-ventilation described above is similar to that carried out by Dr. Kirkbride some years since at his hospital, and in some respects similar to the device of Mr. Rand, in Philadelphia. The principle is briefly this: To create by help of a fire-heated flue a constant upward draught in a pipe which is to be connected to the house-drain, and to stop all the holes which might supply air to the drain, except those by which the drainage itself enters. Then all traps are dispensed with, except that on the main drain outside the house, and air enters the drain at every water-closet, sink, etc., to supply the vacuum created by the aspiration in the heated flue.

When this flue is kept well heated, and all parts of the apparatus are well proportioned, according to the circumstances of the case, it may work well. But if the fire should be allowed to go down, or if not perfectly adjusted, the draught will be insufficient to maintain the excess of inward pressure at all points, and if it fails at any point we have trouble at once. If the draught is weak, some of the inlet-holes will supply the whole - viz., those nearest the point where the suction is applied, while the more remote ones will not get any. This experiment was tried some time ago at the Danvers Asylum, in Massachusetts, and failed on account of the inefficiency of the draught to serve the remote openings.

We notice an unnecessary and foolish complication in the basement, where an air-pipe is arranged so that air can pass quite around the outer trap, thereby dodging it entirely. Why not omit this outer trap, and the air-pipe also, and save their cost? If the trap is really needed to stop the air from passing that point, why put in the by-pass to give it a chance to go just where it might if no trap were there?

We notice, also, that 3-inch pipes are applied as branches from water-closets to main soil-pipe. If such pipes could be made perfectly smooth, and without any offsets or inside ridges at their joints, such a small size might possibly be advisable. But with the ordinary imperfections at joints, we do not think it safe to provide less than 4-inch pipes, although the orifice at the base of a water-closet may safely be restricted to three inches, because whatever is obstructed there is within reach and can readily be removed.

Figure 50.

In any such system which depends upon fire draughts to keep the house free from drain-gas, we must remember that the constant presence of a sufficient fire is an essential part of the scheme, and we must keep that fire burning all summer, night and day, Sundays included. In case such a fire is needed for steam-power, or any other such purpose, it may do very well; but the maintenance of a fire for this special purpose would be rather irksome, and might sometimes be neglected, with very unpleasant results. Moreover, the adjustment of the power of the draught to the sum total of all the inlets is a problem which must be worked out by actual trial in every separate case, and would vary very largely in different conditions of wind and weather, so that an apparatus which would work well during one week might be quite inefficient the next. We should not consider such a system safe, unless a large surplus draught were sure to exist at all times from a fire maintained for some purpose that rendered it positively sure to be constant and unfailing. The use of traps under each sink and water-closet would be entirely inconsistent with this system of ventilation, which demands open orifices.