The corrugated sheaths, made of polyethylene and polypropylene, are employed for the protection of the bulb and the free length; they are provided with thicknesses controlled to the specification of EN 1537-2013 and the DP 12391. They are also made every 500 mm with a thread that allows the joint and the resumption of the same ensuring the tightness.

The smooth sheaths are complying with the requirements of EN 1537-2013 and DP 12391.

The sheaths and plastic pipes must comply with the relevant European standards of product and in particular must be continuous, waterproof, and resistant to aging embrittlement and damage from ultraviolet radiation during storage, transport and installation.

The joints between plastic components must be completely sealed against water penetration, by direct contact or with gaskets.