W. Rogers, Philadelphia, writes:

"I would like to ask a few question regarding the plumbing of tall buildings in a cold climate like that of Chicago. Is the expansion and contraction in the soil pipe sufficient to break out a straight connection as shown at B in the accompanying sketch ? This represents one floor of a 12-story building, the soil pipe being about 175 feet high, hot and cold water to e used, and the plan of other floors being identical with that shown. Would a swing joint like that at C be enough if the closets were not fastened to the floor? Would two swing joints be required if they were fastened to the floor? Is there anything better for an expansion joint than this?"

[We assume that the inquiry refers to wrought-iron pipe. A pipe of this material 175 feet high, exposed to a change of temperature from 300 Fahr. to no degrees, or a difference of 80 degrees, would elongate about 1 inch. If supported at the bottom only, the worst arrangement, the top would move through a space of 1 inch between the extreme temperatures. Assuming the normal temperature to be 70 degrees, there would be a movement at the top of the pipe of one-half an inch upward and one-half downward from the normal position of the pipe. If the lateral connecting with B were absolutely rigid there might be danger of splitting B or springing a joint. As a fact, however, there are modifying conditions. The range of temperatures assumed is probably never experienced; presumably not much more than half the change in temperatures actually occurs. The vertical parts of the building are subjected to very much the same change in temperature as the pipe, and the vertical parts of the entire building move together. The long lateral for the water-closet branches would spring enough to take up the movement in B without injury, and the water-closet branches, if made with lead bends, as is customary and desirable, would take up part of the movement and protect the earthenware of the closets. A further protection can be introduced by supporting the vertical pipe by a clamp half-way up the building, and allowing the expansion to move in both directions-from this middle point instead of supporting at the base. This arrangement reduces the extreme movement at the ends with the range of temperature noted to one-half inch, or one-fourth inch up and down from the normal. The swing joint C referred to seems unnecessary if the laterals are connected with a chance to spring and the verticals are hung in the center of the columns. With the hot-water pipes-it is advisable to use about two expansion loops or expansion fittings in the vertical run. We note a bad rust bend in the drawing at the base of the vent pipe, which should be removed.] the main vent to supply 23 cubic feet a minute would be four times the velocity of discharge in the 4-inch branch, or about 24 feet a second, or 1,440 feet a minute. The resistance in a 2-inch pipe to this air discharge is about one ounce loss of pressure per square inch. The pressure, or weight per square inch of a 2-inch water seal, is about one ounce per square inch. The seal would therefore theoretically just bear the strain. The discharge of additional closets would theoretically syphon adjoining traps. In practice there are other considerations. The sudden discharge of the closets will send a volume of water into the soil branch, which will act like a piston and compress the air in front of it. This will find relief in the lines of least resistance, probably in part through adjoining 2-inch closet vents and in part through the 4-inch soil extension, and when the discharge is past, the air current will be reversed to supply the vacuum at the closets discharged, and an oscillatory movement will follow. In addition to this, the rush of water will act on the ejector principle and carry air with it, and bends and angles in the run of vents will retard the prompt supply of air. These unknown quantities modify the theoretical considerations so materially that the sizes Figured can only be taken as a general guide of minimum sizes. From experience we would advise a 5-inch soil branch, a 5-inch soil extension to the roof, and a 3-inch main vent, especially with syphon closets. The ends of the soil branch should connect with the vent main.