Expansion and contraction caused by uneven heating during storage in the sun may cause the pipe to bow if not restrained by racks. This does not damage the pipe but may be inconvenient when the pipe is taken out of storage for installation
Since black HDPE pipe generally contains greater than 2% carbon black, it will resist damage from sunlight indefinitely. Colored products are compounded with antioxidants, thermal stabilizers and UV stabilizers. Therefore, non-black products should remain in unprotected outdoor storage for no more than two years (or longer only as recommended by the pipe manufacturer). Black products with stripes are generally suitable for unprotected outdoor storage and service.