What's the Difference: Pex Tubing
PEX-a, -b, or -c?
PEX tubing was introduced in Europe in the 1970s but didn’t appear in plumbing installations in the United States until more than a decade later. Since then, however, PEX has grown in popularity as builders, remodelers, and homeowners have realized its benefits over copper. Its flexibility allows it to bend, which reduces the number of connections that need to be made, thereby decreasing opportunities for leaking; it produces no water hammer; heat loss is less; it is more resistant to corrosion and scaling; it is not as susceptible to bursting when frozen; and installation is easier and faster, reducing labor costs.
But there are differences in the way PEX is manufactured. PEX is formed when polyethylene molecules are cross-linked (PEX is an acronym for “polyethylene cross-linked”) through one of three methods. The resulting products are known as PEX-a, PEX-b, and PEX-c. Despite some claims, these designations do not correspond to a rating system on quality but only to how the tubing was manufactured. All three types exceed minimum ASTM requirements and are suitable for plumbing and heating installations. More important than the specific PEX manufacturing process is the dependability of the manufacturer. Look for good customer service and a warranty of at least 25 years.
This method has the highest degree of cross-linking, leading some manufacturers and suppliers to claim that it’s therefore the most uniform, most flexible, and most resistant to kinking and to damage from freezing. It is also typically the most expensive.
Cost: 41¢ to 60¢ per ft.* Sources: Rehau, Uponor
In a recirculating heating system that uses high- temperature chlorinated water, plastic pipes are more susceptible to weakening over time. Although tubing from all three manufacturing methods has met ASTM standards for chlorine resistance, this is the only PEX to have passed the stringent chlorine-recirculating standard of…