Pipe Size Pipe Centre Line80 DN (3”) The minimum bend radius on the pipe centreline shall be 305 mm. Where installations do not permit such as large bend, the maximum obtainable bend radius shall be employed.80 DN (3”), and up to and including 100 DN (4”) The minimum bend radius on the pipe centreline shall be 460 mm. Where installations do not permit such a large bend, the maximum obtainable bend radius shall be employed.125 DN (5”)and greater, proprietary long radius bends Pipe centreline radius of not less than 1.5 times the nominal size in inches may be used.