What is PEX and what makes it different from other plumbing materials on the market?
Crosslinked polyethylene (PEX) is made from high-density polyethylene(HDPE) that has undergone a chemical reaction; through various processes, to bond the molecules together, this process is called crosslinking. PEX is sometimes referred to by type (PEX-A, PEX-B, PEX-C) which has more to do with the process that created it than the actual characteristics of the PEX tubing itself. The three most used methods of crosslinking the HDPE molecules are:
- Peroxide – This is called the Engel Process.
- Moisture-cured Vinylsilane – This is called the Silane Process.
- Beta Irradiation – This is called the Radiation Process.
All PEX is designed to meet temperature and pressure standards set out by the various safety boards, and usually comes rated for 100 Psi @ 180F but must be capable of withstanding a 48 hour period of 150 Psi @ 210F.
PEX water distribution systems are also significantly quieter than rigid piping systems and are less prone to water hammer. PEX tubing is about 180 times less rigid than copper pipe; therefore, it can more readily accept the sudden pressure change associated with water hammer.
PEX tubing has many advantages over other pipes and tubing, but the main attribute that puts it ahead of the others is it’s flexibility. A flexible water line makes installation designs practical that were not possible with rigid piping, such as the “Home Run System”.
PEX tubing; being a plastic, has one serious drawback that must be considered, ultraviolet light will damage exposed PEX tubing if not properly protected with sleeves or installed inside of walls. PEX in contact with sunlight will breakdown, even the ambient light in an unfinished basement will shorten the life expectancy of the tubing.
Pex dimensions
| Nominal Dia |  |
Outside diameter | |
Internal diameter | |
Wall thickness |
| 3/8″ | |
0.5″ | |
0.35″ | |
0.075″ |
| 1/2″ | |
0.625″ | |
0.475″ | |
0.075″ |
| 3/4″ | |
0.875″ | |
0.671″ | |
0.102″ |
| 1″ | |
1.125″ | |
0.865″ | |
0.130″ |
