Polyethylene is a durable material, it is tough, can be laid in bends and is resistant to many chemicals (except for e.g. soap and oil). PE is very well weldable to 100% tensile and watertight connections. It can be used underground and above ground and is frost-resistant. The larger diameters are installed underground because of the stretching and shrinking of PE under the influence of temperature fluctuations. Polyethylene is easily recyclable so better for the environment. PE generally has a thicker wall than for example PVC. This gives extra security and in combination with the toughness of PE also extra safety.