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Repiping with PEX

What is PEX piping?

PEX piping is an innovative new product for hot- and cold-water plumbing systems. PEX is the abbreviation for cross-linked polyethylene (PE-X). It's the result of a production process in which links are formed between polyethylene molecules (thus the name "cross-linked"), forming a network of connected molecules. The result is a material that is highly durable and can withstand high temperatures.

Read more: About PEX Piping |

What is PEX used for?

PEX tubing is widely used to replace copper in plumbing applications. One estimate is that residential use of PEX for delivering drinking water to home faucets has increased by 40% annually, and there is substantial evidence that PEX is or will soon become the dominant technology for carrying water in homes and businesses in the next decade or so. It is widely accepted among different groups, and has been used by volunteer organizations such as Habitat for Humanity in constructing homes. In 2006, the Philadelphia Inquirer recommended that plumbing installers switch from copper pipes to PEX.  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. PEX can be used for underground purposes, although one report suggested that appropriate "sleeves" be used for such applications.

What are the benefits of PEX?

  • Flexibility. PEX has become a contender for use in residential water plumbing because of its flexibility. It can bend into a wide-radius turn if space permits, or accommodate turns by using elbow joints. In addition, it can handle short-radius turns, sometimes supported with a metal brace; in contrast, PVC, CPVC and copper all require elbow joints. A single length of PEX pipe can not handle a sharp 90-degree turn, however, so in those situations, it is necessary to connect two PEX pipes with a 90-degree PEX elbow joint.
  • Direct routing of pipes. PEX can run straight from a distribution point to an outlet fixture without cutting or splicing the pipe. This reduces the need for potentially weak and costly joints and reduces the drop in pressure due to turbulence induced at transitions. Since PEX is flexible, it is often possible to install a supply line directly from the water source to an appliance using just one connection at each end.
  • Greater water pressure at fixtures. Since PEX pipes typically have fewer sharp turns, there is greater water pressure at the sinks and showers and toilets where it is needed.
  • Less materials cost. Cost of materials is approximately 25% of alternatives. One account suggested that the price of copper had quadrupled from 2002 to 2006.
  • Easier installation. Installing PEX is much less labor intensive than copper pipes, since there is no need to use blow torches to solder pipes together, or to use glue to attach pipes to fittings. One home inspector wrote that "Once you've worked with PEX, you'll never go back to that other stinky glue stuff." Builders putting in radiant heating systems found that PEX pipes "made installation easy and operation problem-free." PEX connections can be made by pushing together two matching parts using a compression fitting, or by using an adjustable wrench or a special crimping tool. Generally, fewer connections and fittings are needed in a PEX installation.
  • Reliable. It neither corrodes nor develops so-called "pinhole" leaks.
  • No fire risk during installation. Copper piping required soldering using blowtorches, and there was a risk of flame and heat causing a fire; but with PEX there is virtually no danger from fire. However, there was an unfortunate counter-incident in 2011 in which authorities suspect that six firefighters were injured when a fire melted the plastic PEX pipes, causing water to soak into ceiling insulation, adding greater weight which caused the ceiling to collapse; but the PEX tubing was not blamed as the cause of the fire. Overall PEX piping is much safer to install; according to the U.S. National Fire Prevention Agency, blow torches used for soldering metallic plumbing ranked as one of the "top-ten leading causes of house fires each year."
  • Acceptance by plumbers. There are routinely advertisements for plumbers specifically seeking ones with PEX experience.
  • Ability to merge new PEX with existing copper and PVC systems. Manufacturers make fittings allowing installers to join a copper pipe on one end with a PEX line at the other, as well as have options to reduce or expand the diameter of the pipes.
  • Longevity. The advantageous properties of PEX also make it a candidate for progressive replacement of metal and thermoplastic pipes, especially in long-life applications, because the expected lifetime of PEX pipes reaches 50 years. However, the longest warranty offered by any PEX producer is 25 years.
  • Suitable for hot and cold pipes. A convenient arrangement is to use color coding to lessen the possibility of confusion. Typically, red PEX tubing is used for hot water while blue PEX tubing is used for cold water.
  • Less likely to burst from freezing. The general position is that PEX plastic materials are slower to burst than copper or PVC pipes, but that they will burst eventually since freezing causes water to expand. One account suggested that PEX water-filled pipes, frozen over time, will swell and tear; in contrast, copper pipe "rips" and PVC "shatters". Home expert Steve Maxwell suggested in 2007 that PEX water-filled pipes could endure "five or six freeze-thaw cycles without splitting" while copper would split apart promptly on the first freeze. In new unheated seasonal homes, it is still recommended to drain pipes during an unheated cold season or take other measures to prevent pipes from bursting because of the cold. In new constructions, it is recommended that all water pipes be sloped slightly to permit drainage, if necessary.
  • No corrosion. Copper and iron pipes can experience corrosion leaks but PEX does not have these problems.
  • Environmental benefits. One account suggested that PEX used in radiant heating was better for the environment than a copper choice, although it noted that the pipes were based on petroleum products.
  • Pipe insulation possible. Conventional foam wrap insulation materials can be added to PEX piping to keep hot water hot, and cold water cold, and prevent freezing, if necessary.

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