Answer: depending on your budget and the different characteristics of the material, in particular its solidity and its conduction capacity.
The cheapest material is polyvinyl chloride (PVC). It is however not recommended, being favorable for the development of bacteria and being able to give off a foul odor. Not to mention the risk of toxic fumes during hot weather. At almost the same price, polyethylene is a much better choice for small purses. Good thermal conductor and without risk to health, it is also unfortunately not very solid. Concrete and baked brick have good conductivities but the intrusion of pollutants into the pipes is possible. Ductile iron, a little more expensive, solid and good conductor, requires elastomer seals and an anticorrosion treatment of the external walls. High density polyethylene is expensive and widely used because it is well suited to this type of construction. But the palm of the ideal material goes to polypropylene. Resistant, seven times more conductive than PVC, lined with an antibacterial layer. There is nothing better, but quality has to be paid for ... You too, send us your DIY question