Cross-linked polyethylene is more commonly known as PEX. This type of plastic tubing (PEX) is created from high density polyethylene, commonly referred to as HDPE. The high density polyethylene undergoes a melting process and then it is subjected to extrusion.
Europeans have been installing PEX systems for over three decades, in the USA they have been utilising this type of pipework for between ten and fifteen years. PEX has become so popular because the piping is easy to install, fairly inexpensive and it is reliable. PEX piping offers great flexibility and it wears well in extremely low temperatures. CVPC and copper piping tends to cost far more than the polyethylene tubing and being less flexible than PEX tubing, it is harder to work with too.
Different types of PEX
PEX-a, PEX-b, PEX-c. Each of the three grades is made in a different way.
• PEX-a is the most durable and the most uniform of the three grades, it is made using a process known as the Engel method.
• PEX-b is manufactured using a process called the Silane method. When PEX-b has been installed it has the same properties as PEX-a.
• PEX-c is manufactured in a reasonably environmentally friendly way, the manufacturing process involves the use of an electronic beam.
PEX can withstand high temperatures, as high as two hundred degrees. This makes the tubing ideal for using in conjunction with radiant or hydronic heat systems such as underfloor heating. Copper tubing has always been popular but PEX popularity continues to grow due to is flexibility.
PEX piping is made in two colours, red tubing for hot lines and blue piping for cold lines. Ferrous system parts are prone to rust but PEX piping has an inbuilt oxygen barrier to ward off rust. Large piping has become more popular since tools and fittings have become easy to access but the tubing is available in the following sizes - one quarter inch to four inch.
PEX piping can be utilised underground, this makes the piping a highly attractive proposition. Coils of PEX can be as small as one hundred feet long or as large as one thousand feet long. Straight lengths of the tubing range between ten and twenty feet in length.
It is not uncommon to see a manifold added to the PEX structure, the manifold functions as the centrepiece and all of the PEX lines run into that manifold.
If a manifold is integrated into a radiant heat system then this is the point where all loops meet.
Many plumbing systems have what is commonly referred to as a "Home Run system", in general this is the central manifold or it could refer to numerous smaller manifolds running around the home.
PEX tool and fitting systems incorporate expanders, presses, clamps, crimps, and lastly compression. The crimp or the clamp are the most popular fitting tool used, this entails using copper crimp rings with barbed fittings and clamps that are made from stainless steel.