Cross-linked polyethylene, commonly abbreviated PEX or XLPE, is a form of polyethylene with cross-links. It is formed into tubing, and is used predominantly in building services pipework systems, hydronic radiant heating and cooling systems, domestic water piping, and insulation for high tension (high voltage) electrical cables. PEX has proven to be a successful alternative to traditional types of plumbing systems, such as copper and CPVC. The growing popularity of PEX plumbing systems is certainly due in part to its “green” potential. PEX is green in the following categories: durability, water conservation, energy efficiency, and health and safety.
For more than 30 years, PEX has undergone extensive testing and material performance, making it one of the most heavily tested piping materials in the world. Based on these tests, it has proven to be an extremely durable material.
- PEX doesn’t experience corrosion, mineral build-up, abrasion, filming, pitting, and electrolysis, issues that are typically associated with metal piping.
- PEX is resistant to freeze damage, because it expands and contracts as water freezes and thaws inside the tubing, avoiding costly ruptures.
- PEX has the potential for fewer connections, reducing the chance of experiencing leaks, which typically occur at the connections within a plumbing system.
PEX home-run systems have the potential to conserve water if they’re designed and installed properly. They help conserve water by reducing the amount of time it takes for hot water to arrive at a fixture. As a result, homeowners don’t have to run the water as long while waiting for it to warm up. According to a test conducted by the NAHB Research Center, home-run systems save 30% to 40% more water and time over their trunk-and-branch and remote manifold cousins.
- With a home-run system design, there are direct lines between the hot water manifold and individual fixtures. This reduces the amount of water that must be purged from a line before hot water will arrive at the fixture. Placing the manifold in a central location in the home can further reduce the length of lines.
- With a home-run system design, direct lines can be sized according to the requirements of each fixture. Manufacturers recommend the use of 3/8” tubing whenever possible, which is the smallest diameter available for PEX; a smaller diameter reduces the amount of time it takes for hot water to arrive at a fixture.
PEX plumbing systems have the potential to save energy, which translates to a lower energy bill for homeowners.
- PEX decreases the amount of energy used by the water heater, because hot water arrives at fixtures faster. This is particularly true of home-run system designs that have the hot water manifold in a central location.
- PEX has a higher R-value than other materials, which reduces the amount of heat lost from the water as it travels through the piping. Hot water stays hot, and cold water stays cold.
- PEX has fewer connections than other types of plumbing systems due to its flexible nature. This is particularly true of the home-run and remote manifold system designs. Connections add to the effective length of piping, increasing the time it takes for hot water to reach fixtures.
- PEX has mechanical fittings, rather than fittings that require the use of propane torches, helping to conserve energy on the job site.
Health and safety
PEX plumbing systems are great for transporting potable water, as PEX is an inert, non-toxic material that doesn’t contaminate the water passing through it. It also offers the following benefits.
- PEX is manufactured according to the strict standards of ASTM and CSA International. It’s also regularly tested and certified by national certification agencies like NSF International and Underwriters Laboratories. PEX complies with the NSF/ANSI Standard 61 for drinking water health effects.
- PEX has mechanical fittings, which don’t require solvents or chemicals that might leach into the water when the system is first used.
- PEX doesn’t experience corrosion or mineral build-up, which can occur with other types of plumbing systems.
- PEX doesn’t require flame, solder, or flux to install it, resulting in zero volatile organic compound (VOC) emissions.