─────────────────┬─────────────────┬─────────────────┬───────────────── Diameter of │Cubic Contents of│ Amount of Water │Area of Pipe 1728 Circular Pipe or │ Gas in each 100 │to produce 1 inch│ = 1 cubic foot. Drain. │ feet length of │rise of Liquid in│ │ Drain Pipe or │ Detector. │ │ Sewer. │ │ ─────────────────┼─────────────────┼─────────────────┼───────────────── ins. │ cub. ft. │gals. pts. ozs. │ 4│ 8–1255/1728│ 0 1 7│ 12·566 6│ 19–1096/1728│ 0 4 0│ 28·274 9│ 44–308/1728│ 1 1 2│ 63·617 12│ 78–932/1728│ 2 0 5│ 113·097 15│ 122–1242/1728│ 3 1 6│ 176·715 18│ 176–1234/1728│ 4 5 0│ 254·469 19│ 196–1546/1728│ 5 1 1│ 283·529 20│ 218–288/1728│ 5 5 7│ 314·160 21│ 240–913/1728│ 6 2 1│ 346·361 22│ 263–1695/1728│ 6 7 0│ 380·133 23│ 288–917/1728│ 7 4 2│ 415·476 24│ 314–276/1728│ 8 1 6│ 452·390 25│ 340–1530/1728│ 8 7 0│ 490·875 26│ 368–1212/1728│ 9 4 13│ 530·930 27│ 397–1063/1728│ 10 2 14│ 572·556 28│ 427–1147/1728│ 11 1 12│ 615·753 29│ 458–1201/1728│ 11 7 8│ 660·521 30│ 490–1512/1728│ 12 6 9│ 706·860 ─────────────────┴─────────────────┴─────────────────┴───────────────── The method of testing drains and fittings by compression of gas is as follows:—When the drainage plan of a building exists, the work of testing by compression of gas in the drain will be a very simple matter. Plate 1 shows the drains as laid to a semidetached villa, with two inlets from sinks marked 1, one from bath overflow marked 2, and two from the soil-pipes of closets in the basement and first-floor marked 3. The drain from A to B is a 6-inch stoneware pipe, and its length is 100 feet. The amount of gas in it would be 19–1096/1728 cubic feet. The branch drains from the other inlets are 4 inches in diameter, and the collected lengths are 50 feet, and the quantity of gas in them would be 4–627/1728 cubic feet, giving a total in the whole of the drain of nearly 24 cubic feet.