PEX Plumbing and Radiant Heat...Type A B Or C....Do You Know The Difference
PEX Water Systems and Radiant Heat Systems are the best this industry has ever seen. A lot has changed in the 30 plus years I have been helping people with their plumbing installation and repair questions.
From the days of Galvanized Iron Pipe with its corrosion issues and CPVC with its pinhole leak and freeze crack problems (CPVC is still available but not allowed by many codes) to the still popular L & M series copper. M copper is a ridged product usually sweated with fittings while L copper is a softer coil that can be sweated, flared or compression fitted.
This brings us to the heart of this article, PEX which stands for Poly Ethylene Cross (X)-Linked tubing. It is the cross-linking process that makes PEX strong, safe and reliable, and it is how this process is done that determines what grade, or category, the PEX belongs to.
There are 3 grades or types of PEX listed as Types A, B, and C. The letter designation tells you how the product was created and what properties you can expect with each type including the flexibility, strength, and uniform nature of the material.
PEX-A is made using the Engel (or peroxide) method to crosslink the molecules of polyethylene. With this method, the crosslinking is done at a high temperature above the melting point of the crystals. The Engel method produces the strongest, most flexible PEX tubing possible. PEX-A also features a strong thermal memory and freeze protection. Since this process takes more time and more sophisticated equipment, PEX-A products seem to be the most expensive type. AquaPEX is the only PEX-A material available for plumbing applications. While examples of PEX-A for radiant heat include ThermaPEX and hePEX.
PEX-B is made using the Silane (or moisture cure) method. This method performs the crosslinking with a chemical agent where the process is accelerated using heat and moisture. This chemical crosslinking is susceptible to some areas where the bonds are weaker than others and a slightly stiffer final product than PEX-A. Examples of PEX-B include Viega PEX, HydroPEX , and Watts PEX.
PEX-c is made using the Electron beam (or radiation) method. This method passes the polyethylene under an electron beam multiple times in order to get to the desired level of crosslinking. This is the most energy-efficient method of creating PEX, but often results in a more brittle, less consistent product than either PEX-A or PEX-B. Electron beam is also the least expensive process so therefore creates the least expensive tubing.
Choosing which type is best for your project should come down to looking at how the system will be run. If you will have many bends in your system or if your system will be in an area of freeze concerns then it is probably best to spend a few extra dollars for PEX-A tubing.
When it comes to lay-out of your system there are 5 basic lay-out designs. The Home Run Installation uses central manifolds with all runs returning directly to it.
In the Remote Manifold Installation, a pair of closed ended manifolds for hot and cold are placed near each grouping of fixtures such as a bathroom with a pair of closed ended manifolds at each primary grouping area.
While in the Structured Plumbing Installation the set up is similar to Remote Manifold except the hot water manifold is open ended and acts as a recirculation system for more on demand type delivery. This system is considered to be very energy efficient since its recalculating properties provide the best on demand hot water option thus saving water usage and energy.
The Modified Home Run Installation is similar to Home Run but with a series of manifolds usually open ended to reduce the quantity of tubing required.
The last option is the Run and Branch System which is most like the old Copper and CPVC installations where a line is split with a tee or elbow to connect each fixture in the line.
No matter what system you install be sure to pressure test the complete system with 40 to 60 pounds of air pressure before opening the system to water usage.
There are a variety of fitting and tool options available including the PEX Crimping System, PEX Clamping System, and the SharkBite fitting system. I cover each system as well as which types of tubing work best with each fitting system and which are the most DIY friendly in the detailed pages on PEX Water Systems and PEX Radiant Heat Systems of my Homebuilding Questions web site.
If you have found one PEX tubing type works better for you than another please leave us a comment to help other readers.
From the days of Galvanized Iron Pipe with its corrosion issues and CPVC with its pinhole leak and freeze crack problems (CPVC is still available but not allowed by many codes) to the still popular L & M series copper. M copper is a ridged product usually sweated with fittings while L copper is a softer coil that can be sweated, flared or compression fitted.
This brings us to the heart of this article, PEX which stands for Poly Ethylene Cross (X)-Linked tubing. It is the cross-linking process that makes PEX strong, safe and reliable, and it is how this process is done that determines what grade, or category, the PEX belongs to.
There are 3 grades or types of PEX listed as Types A, B, and C. The letter designation tells you how the product was created and what properties you can expect with each type including the flexibility, strength, and uniform nature of the material.
PEX-A is made using the Engel (or peroxide) method to crosslink the molecules of polyethylene. With this method, the crosslinking is done at a high temperature above the melting point of the crystals. The Engel method produces the strongest, most flexible PEX tubing possible. PEX-A also features a strong thermal memory and freeze protection. Since this process takes more time and more sophisticated equipment, PEX-A products seem to be the most expensive type. AquaPEX is the only PEX-A material available for plumbing applications. While examples of PEX-A for radiant heat include ThermaPEX and hePEX.
PEX-B is made using the Silane (or moisture cure) method. This method performs the crosslinking with a chemical agent where the process is accelerated using heat and moisture. This chemical crosslinking is susceptible to some areas where the bonds are weaker than others and a slightly stiffer final product than PEX-A. Examples of PEX-B include Viega PEX, HydroPEX , and Watts PEX.
PEX-c is made using the Electron beam (or radiation) method. This method passes the polyethylene under an electron beam multiple times in order to get to the desired level of crosslinking. This is the most energy-efficient method of creating PEX, but often results in a more brittle, less consistent product than either PEX-A or PEX-B. Electron beam is also the least expensive process so therefore creates the least expensive tubing.
Choosing which type is best for your project should come down to looking at how the system will be run. If you will have many bends in your system or if your system will be in an area of freeze concerns then it is probably best to spend a few extra dollars for PEX-A tubing.
When it comes to lay-out of your system there are 5 basic lay-out designs. The Home Run Installation uses central manifolds with all runs returning directly to it.
In the Remote Manifold Installation, a pair of closed ended manifolds for hot and cold are placed near each grouping of fixtures such as a bathroom with a pair of closed ended manifolds at each primary grouping area.
While in the Structured Plumbing Installation the set up is similar to Remote Manifold except the hot water manifold is open ended and acts as a recirculation system for more on demand type delivery. This system is considered to be very energy efficient since its recalculating properties provide the best on demand hot water option thus saving water usage and energy.
The Modified Home Run Installation is similar to Home Run but with a series of manifolds usually open ended to reduce the quantity of tubing required.
The last option is the Run and Branch System which is most like the old Copper and CPVC installations where a line is split with a tee or elbow to connect each fixture in the line.
No matter what system you install be sure to pressure test the complete system with 40 to 60 pounds of air pressure before opening the system to water usage.
There are a variety of fitting and tool options available including the PEX Crimping System, PEX Clamping System, and the SharkBite fitting system. I cover each system as well as which types of tubing work best with each fitting system and which are the most DIY friendly in the detailed pages on PEX Water Systems and PEX Radiant Heat Systems of my Homebuilding Questions web site.
If you have found one PEX tubing type works better for you than another please leave us a comment to help other readers.