(_i_) Insecure attachment of branches or spurs. _Workmanship and Finish_ (29) Pipes shall be substantially free from fractures, large or deep cracks and blisters, laminations and surface roughness. (31) The glaze shall consist of a continuous layer of bright or semi-bright glass substantially free from coarse blisters and pimples.... Not more than 10 per cent of the inner surface of any pipe barrel shall be bare of glaze except the hub, where it may be entirely absent. Glazing will not be required on the outer surface of the barrel at the spigot end for a distance from the end equal to ⅔ the specified depth of the socket for the corresponding size of pipe. Where glazing is required there shall be absence of any well defined network of crazing lines or hair cracks. (32) The ends of the pipe shall be square with their longitudinal axis. (33) Special shapes shall have a plain spigot end and a hub end corresponding in all respects with the dimensions specified for pipes of the corresponding internal diameter. TABLE 36 PROPERTIES OF CLAY SEWER PIPE Abstracts from Tentative Specifications of the American Society for Testing Materials ─────────┬─────────┬───────────┬───────┬────────┬──────┬──────┬───────── Internal │ Minimum │ Maximum │Laying │Diameter│Depth │Taper │ Minimum Diameter,│Crushing │Absorption,│length,│ of │ of │ of │Thickness Inches │Strength,│ Per Cent │ Feet │ Inside │Socket│Socket│ of │ Pounds │ │ │ of │Inches│ │ Barrel. │ per │ │ │Socket, │ │ │ Inches │ Linear │ │ │ Inches │ │ │ │ Foot. │ │ │ │ │ │ │See Note │ │ │ │ │ │ │ 2 │ │ │ │ │ │ ─────────┼─────────┼───────────┼───────┼────────┼──────┼──────┼───────── │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ ─────────┼─────────┼───────────┼───────┼────────┼──────┼──────┼───────── │ │ │ │ │ │ │ │ │ │ │ │ │ │ ─────────┼─────────┼───────────┼───────┼────────┼──────┼──────┼───────── 6 │ 1430 │ 5 │2, 2½, │ 8¼ │ 2 │1 : 20│ ⅝ │ │ │ 3 │ │ │ │ 8 │ 1430 │ 5 │2, 2½, │ 10¾ │ 2¼ │1 : 20│ ¾