PEX

PEX is a flexible piping material made from crosslinked polyethylene. The crosslinking enhances the polymer’s temperature and pressure resistance, chemical stability, and durability, making it suitable for potable water distribution, radiant floor heating, and other plumbing applications. Its flexibility allows long, continuous runs with fewer joints compared to rigid pipes.

There are three main crosslinking methods used to produce PEX: PEX-A, PEX-B, and PEX-C. PEX-A uses peroxide crosslinking (Engel method); PEX-B uses a silane-based moisture cure process; PEX-C employs irradiation. These methods yield materials with different properties in terms of elasticity, memory, and chemical resistance, which can influence installation choices and cost.

Applications and installation methods: PEX tubes are used for hot and cold potable water and for hydronic heating systems. They are installed with fittings such as crimp, clamp, or expansion systems, enabling fewer joints and faster installation. PEX is praised for its resistance to scale and corrosion, quiet operation, and ease of handling. It is widely accepted in many building codes, though local requirements and temperature/pressure ratings defined by manufacturers apply.

Limitations and considerations: PEX is sensitive to ultraviolet light and should be kept away from sun exposure. Some systems require an oxygen barrier for radiant heating. Temperature and pressure ratings vary by product, and certain chemical exposures or prolonged high temperatures can affect performance. Underground use is possible with appropriate protection and adherence to code requirements in the relevant jurisdiction.

Standards and regulation: In the United States, PEX potable water piping is standardized by ASTM F876 and F877; in Canada by CSA B137.5; in Europe by EN ISO 15875. Codes and approvals vary by country and locality.

History: PEX development progressed through the late 20th century, with broader adoption in plumbing and heating systems in subsequent decades.