N.Y. Comp. Codes R. & Regs. tit. 16, § 255.313 – Bends and elbows.

(a) Each field bend in steel pipe must comply with the following criteria:
1. (1) A bend must not impair the serviceability of the pipe.
2. (2) Each bend must have a smooth contour and be free from buckling, cracks, or any other mechanical damage.
(b) On pipe containing a longitudinal weld, the longitudinal weld must be as near as practicable to the neutral axis of the bend unless:
1. (1) the bend is made with an internal bending mandrel; or
2. (2) the pipe is 12 inches (305 millimeters) or less in outside diameter or has a diameter to wall thickness ratio less than 70.
(c) Each circumferential weld of steel pipe which is located where the stress during bending causes a permanent deformation in the pipe must be nondestructively tested after the bending process.
(d) An operator may not install plastic pipe with a bend radius that is less than the minimum bend radius specified by the manufacturer for the diameter of the pipe being installed.
(e) An operator may not install plastic pipe with a bend radius that is less than the minimum bend radius specified by the manufacturer for the diameter of the pipe being installed.