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PEX (or crosslinked polyethylene) is part of a water supply piping system that has several advantages over metal pipe (copper, iron, lead) or rigid plastic pipe (PVC, CPVC, ABS) systems.

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PEX tubing has been widely known and popularly used in Europe for many years (PEX plumbing has been in use in Europe since 1970) with problems rarely encountered.

PEX has a 3-dimensional molecular bond that offers advantages over metal pipes such as: Resistance to heat deformation, chemicals, scratching, shrinkage, stress cracks, and abrasion. Constant water flow and pressure is ensured with the use of PEX pipes.

It is flexible, resistant to scale and chlorine, doesn’t corrode or develop pinholes, is faster to install than metal or rigid plastic, and has fewer connections and fittings.

PEX tubing is made from crosslinked HDPE (high density polyethylene) polymer. The HDPE is melted and continuously extruded into tube.

The crosslinking of the HDPE is accomplished in one of three different methods.

Flexible PEX tube is manufactured by extrusion, and shipped and stored on spools, where rigid plastic or metal piping must be cut to some practical length for shipping and storage.

This leads to several advantages, including lower shipping and handling costs due to decreased weight and improved storage options.

PEX plumbing installations require fewer fittings than rigid piping. The flexible tubing can turn 90 degree corners without the need for elbow fittings, and PEX tubing unrolled from spools can be installed in long runs without the need for coupling fittings.

Attaching PEX tube to fittings does not require soldering, and so eliminates the health hazards involved with lead-based solder and acid fluxes; PEX is also safer to install since a torch is not needed to make connections.

PEX resists the scale build-up common with copper pipe, and does not pit or corrode when exposed to acidic water.

PEX is much more resistant to freeze-breakage than copper or rigid plastic pipe.

PEX tubing does not transfer heat as readily as copper, and so conserves energy.

Water flows more quietly through PEX tube, and the characteristic “water hammer” noise of copper pipe systems is virtually eliminated.

PEX plumbing installations cost less because PEX is less expensive than copper pipe.

It take less time spent running pipe and installing fittings than with rigid pipe systems and installing fewer fittings reduces the chances for expensive callbacks.

PEX tubing is widely used to replace copper in plumbing applications.

In the twentieth century, the first plumbing pipes were made from galvanized steel water pipes, but users experienced problems with the internal build-up of rust which reduced water volume, but these were replaced by copper pipes in the late 1960s.

Plastic pipes with fittings using glue were used as well in later decades. Initially PEX tubing was the most popular way to transport water in hydronic radiant heating systems, and it was used first in hydronic systems from the 1960s onwards.

Hydronic systems circulate water from a boiler or heater to places in the house needing heat, such as baseboard heaters or radiators.

PEX is suitable for recirculating hot water.Gradually PEX became more accepted for more indoor plumbing uses, such as carrying pressurized water to fixtures throughout the house.

Increasingly, in the 2000s, copper pipes as well as plastic PVC pipes are being replaced with PEX.

– Crosslinking is a chemical reaction that occurs between polyethylene polymer chains. Crosslinking causes the HDPE to become stronger and resistant to cold temperature cracking or brittleness on impact while retaining its flexibility. The three methods of crosslinking HDPE are the Engels method (PEX-a), the Silane Method (PEX-b), and the Radiation method (PEX-c). Several industry participants claim that the PEX-a method yield more flexible tubing than the other methods. All three types of PEX tubing meet the ASTM, NSF and CSA standards.

Source : pexinfo.com and small-house-building.com

(this article published in 1BINA.my)