N.Y. Comp. Codes R. & Regs. tit. 16, § 255.321 – Installation of plastic pipe.

(a) Plastic pipe must be installed below ground level unless otherwise permitted in subdivisions (l), (m) and (n) of this section.
(b) Plastic pipe that is installed in a vault or any other below grade enclosure must be completely encased in gas-tight metal pipe and fittings that are adequately protected from corrosion.
(c) Plastic pipe must be installed so as to minimize shear or tensile stresses.
(d) Plastic pipe must have a minimum wall thickness in accordance with section 255.121 of this Part.
(e) Plastic pipe that is not encased must have an electrically conductive wire or other approved means of locating the pipe. Tracer wire may not be wrapped around the pipe and contact with the pipe must be minimized but is not prohibited. Tracer wire or other metallic elements installed for pipe locating purposes must be resistant to corrosion damage, either by use of coated copper wire or by other means.
(f) Plastic pipe that is being encased must be inserted into the casing pipe in a manner that will protect the plastic. Plastic pipe that is being encased must be protected from damage at all entrance and all exit points on the casing. The leading end of the plastic must be closed before insertion. The casing must be prepared to the extent necessary to remove sharp edges, projections, or abrasive material which could damage the plastic.
(g) Care shall be exercised to avoid rough handling of plastic pipe and tubing. It shall not be pushed or pulled over sharp projections, dropped or have other objects dropped upon it.
(h) Caution shall be taken to prevent kinking or buckling, and any kinks or buckles which occur shall be removed by cutting out as a cylinder.
(i) Squeeze-offs of plastic may be made to control flows in accordance with manufacturer's recommendations and a proven procedure without replacement of the pipe section. However, each squeeze-off must be adequately marked on the pipe to preclude further squeeze-off at that location.
(j) The piping shall be installed with sufficient slack to provide for possible contraction. Cooling may be necessary before the last connection is made under extremely high temperature conditions.
(k) That portion of the plastic piping exposed due to the removal of a section of the casing or which spans disturbed earth shall be of sufficient strength to withstand the external loading and shearing forces or it shall be protected with a suitable bridging piece.
(l) Uncased plastic pipe may be temporarily installed above ground level under the following conditions:
1. (1) The operator must be able to demonstrate that the cumulative above ground exposure of the pipe does not exceed the manufacturer's recommended maximum period of exposure or two years, whichever is less.
2. (2) The pipe is located where damage by external forces is unlikely or is otherwise protected against such damage.
3. (3) The pipe adequately resists exposure to ultraviolet light and high and low temperatures.
(m) Plastic pipe may be installed on bridges provided that it is:
1. (1) installed with protection from mechanical damage, such as installation in a metallic casing;
2. (2) protected from ultraviolet radiation; and
3. (3) not allowed to exceed the pipe temperature limits specified in section 255.121 of this Part.
(n) Plastic mains may terminate above ground level provided they comply with the following:
1. (1) The above-ground level part of the plastic main is protected against deterioration and external damage.
2. (2) The plastic main is not used to support external loads.
3. (3) Installations of risers at regulator stations must meet the design requirements of section 255.204 of this Title.