Q. We have a job of work which was done according to the inclosed plan. We would like you to inform us, if possible, why it is that there should be a smell of sewer-gas through the bath-tub pipe. A is the soil-pipe, which is extended through the roof; the sewer in the cellar is carried to the chimney, and run up next to a hot flue to the top of chimney. B is a 2-inch vent - pipe from closet-trap. C is a plunger-closet, with a trap. D is a lead trap under the trap of the water-closet. E, waste-pipe from bath-tub to water-closet trap, which is taken out above the water-line. F is the 1 1/4 -inch vent-pipe from the bath-tub trap. G, overflow of bath - tub where the sewer - gas smell is the strongest. H, waste from bath-tub, through which there is some smell. I, bathtub. None of the traps syphon out, for we have tried them thoroughly. Almost instantly after pouring in water the smell comes up through the opening H and I. We would like very much to have you explain, if possible.

A. The overflow-pipe does not seem to enter the dip of the bath-tub trap, which permits a circulation of air down H and out at G, or vice versa. The smell, you will doubtless find, is caused by the fouling of the overflow-pipe. It is possible this smell is produced by servants rinsing out bedroom vessels in the bath-tub. Heat a flat-iron and place it against the overflow, and see if you can detect a smell of urine. It is, of course, presumed that no drainage enters the soil-pipe A above the vent-pipes B and F.

Figure 6i.

On the foregoing reply a correspondent writes:

"While you suggest a probable cause, I don't think you go far enough. In the first place, the person lifts the handle of the water-closet, which has a large body of water discharging instantly into the soil-pipe. This heavy plunge of water drives the air before it with such a pressure as to force the confined air (between the trap of water-closet and the trap D, shown on the plan) through the trap of the bath. As the air-pipe from the bath-trap, under the circumstances, is entirely too small to allow the compressed air, caused by discharge of water-closet in the confined space between the two traps, free vent, it therefore finds vent through trap of the bath, the waste of which appears on the sketch to be larger than the air-pipe from the same.

"The proper remedy is to take the lower trap D out entirely, and give the soil-pipe of the water-closet a free vent into the main sewer. What the plumber put the lower trap in for is beyond my comprehension, and the sooner it is removed the better. I presumed, as you did, that nothing empties into the soil-pipe above the vent-pipes F and B, for in that case the vents would be of no use whatever, as they would, in all probability, be stopped up by slime and filth."

We quite agree with our correspondent that the lower trap D should be removed, and his theory of the cause seems reasonable, although similar complaints are frequently made, and the cause has been traced to the source indicated. As this particular style of water-closet holds only 1 1/8 gallons of water, and that is discharged through a side-outlet 3 1/2 inches in diameter, consuming a little time in its delivery, it is a question whether with the vent-pipes F and B, 1 1/4 and 2 inches respectively, the compression of air could be so sudden as to greatly displace the water in the bath-tub trap. Moreover, the space between the two traps, ventilated as shown, and frequently flushed, could hardly be as foul as our correspondent intimates. The lower trap, however, should not be there, and it was a neglect on our part in not advising its removal.