Supply Pipe - Plastic - Part III: A CLOSER LOOK AT PEX
This is an updated version of the product training course introduced by Supply House Times in 1979, authored by Don Arnold.
Since PEX is the newest and fastest-growing material in common use for supply piping today, we are going to devote this segment to a closer look. (This will take us a bit beyond just the supply piping applications we have been examining in the preceding articles, since PEX has significant use in heating and refrigeration systems, as well.) PEX, short for crosslinked polyethylene, has become the most widely used flexible plastic piping material suitable for both hot and cold supply applications. Originally developed and used in Europe (since way back in the 60s), its use in this country was pretty much limited to non-plumbing applications until the mid-90s. Those initial uses included hydronic radiant, snow-melting, ice rink and refrigeration systems. Until that time, polybutylene (PB) had been the flexible plastic piping material of choice, but when massive field failures finally forced that off the market, the door swung wide open for an alternative.
The succeeding heir, PEX, is composed of high-density polyethylene which undergoes a physically or chemically induced molecular change by one of several processes. Manufacturers explain the result as a three-dimensional "bridging" or "networking" of molecules that form a thermoelastic material, stable at high temperatures while retaining flexibility and resistance to chemical attack. Translation for the rest of us: the stuff is stronger and more durable than regular PE under a wide range of temperature extremes (up to 180?F for plumbing supply applications and 200?F for others).