PEX is a cross-linked polythene that has different types depending on the manufacturing process. Some of the types of PEX include PEX A, PEX B, and PEX C. The most common types are PEX A and PEX B.
What is PEX A?
PEX A is a type of PEX tube that is manufactured by the use of the peroxide method. In this method, high-density polyethylene is melted and free radicals are created to form cross-links that appear between molecules. The process is done at high temperatures exceeding the decomposition temperature of the polymer.
What is PEX B?
PEX B is a type of PEX tube that is manufactured by the use of the silane method to cross-link the molecules. The silane process is the most used method since there is an improved compatibility of the tube. The process is done by extruding using a catalyst and exposing the tube to hot water.
Advantages of PEX A VS PEX B
Let’s explore these types of plumbing materials:
Advantages of PEX A
- PEX A has limited flow resistance due to the use of a joining method that has a fitting with the same diameter as the pipe.
- PEX A has a higher flexibility compared to that of PEX B.
- The coil memory of PEX A is low hence returns to its original form after bending or coiling.
- PEX A has a higher rate of cross-link compared to that of PEX B. This improves the chemical and temperature performances.
Disadvantages of PEX A
Shrinking of the pipe that is done after joining takes longer in areas with low temperatures. This can be fastened by the use of a heat gun.
Furthermore, PEX A is very expensive compared to PEX B.
Advantages of PEX B
- PEX B is cheaper compared to PEX A.
- Usually is resistant to chlorine and oxidation.
- Joining fittings is easy since there is no need to use a tool.
Disadvantages of PEX B
There is a reduction in diameter size when joining since the fitting is usually smaller in size compared to the pipe.
Due to the smaller diameter of the fittings, there is increased resistance flow and volume of water flowing.
The cross-link ratio is of a low degree compared to PEX A which results in a stiffer pipe with a higher coil memory.
PEX A and PEX B Manufacturing Process
PEX A is manufactured by the use of the peroxide method. In this method, high-density polyethylene is melted and free radicals are created to form cross-links that appear between molecules. The process is done at high temperatures exceeding the decomposition temperature of the polymer.
PEX B is manufactured by the use of the silane method to cross-link the molecules. The silane process is the most used due to the improved compatibility of the tube. The process is done by extruding using a catalyst and exposing the tube to hot water.
Difference between PEX A and PEX B
PEX A is produced by the peroxide method while PEX B is produced by the silane method. Additionally, PEX A joining uses expansion-style fittings while PEX B uses insert-style fittings.
Fittings are inserted by use of an expansion tool while PEX B fittings are inserted manually but pushed into the pipe.
Similarities Between PEX A and PEX B.
All PEX pipes are usually manufactured to meet equal performing standards. Some of the standards are as follows:-
- ASTM F876 regulates the standards necessary for all PEX tubing.
- NSF/ANSI/CAN61 regulates standards used for pipes in water distribution systems.
- If pipe is used for portable water the pipe must meet standards of ANSI/NSF16 AND ANSI/NSF372.
- For lead-free pipes must meet the PW-G and NSF-61-G.
- For use of chlorinated water, the pipes must meet the ASTM F2023 standards.
- If a pipe is used for radiant floor heating, ANSI/NSF 14 standards must be met.
PEX A vs. PEX B Material Designation Code
The designation code is used to show the chlorine and UV resistance. The code is broken down into three parts or classes.
- First digit represents the chlorine resistance and is up to a maximum of 5.
- Second digit represents the Ultraviolet resistance which is up to a maximum of 3.
- Last two digits represent HDB which is 06 for most pipes. This represents 630HDB.
Usually, the highest rating of a PEX tube is PEX 5306.
Conclusion
In conclusion, PEX is a cross-linked polyethylene that has different types depending on the manufacturing process. PEX A tube is most commonly used since it is flexible and has low amounts of faults because of the low flow resistance. PEX B is reconsidered in case one wants to choose a cheaper option.