OPUS

Domestic Water: PEX Tubing

Domestic hot and cold water systems generally convey potable hot and cold water used for...
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Cross-Linked Polyethylene (PEX) is a thermoset material made from medium or high density,...
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Benefit of Material to Systems Application

PEX piping has been used in hot and cold water distribution systems and for hydronic radiant heating in Europe for many years. Introduced into the United States in the 1980s, PEX has replaced polybutylene (PB) as the most widely used flexible plumbing piping. With the recent cost increases for copper and escalating theft of copper from job sites, plastic piping alternatives such as PEX have become more appealing. PEX plumbing systems consist of not only tubing, but fittings, valves, manifolds, tools, risers, accessories and transition fittings - everything you need to get the job done. Cost saving benefits of PEX include lower installed cost, fewer fittings, less labor and decreased potential for leaks. It is flame-free, safe, easy to handle, and easy to learn. PEX tubing is recognized as acceptable for water distribution piping in all major model plumbing codes. PEX systems are well suited to multiple layouts, such as manifold, remote manifold and traditional trunk and branch.

System Application and Material Usage

PEX tubing can be used in potable water distribution systems provided it has been tested in accordance with the governing standard, meets the requirements of ANSI/NSF Standard 61, and bears proper certification from a recognized testing agency.

Cross-linked polyethylene (PEX) materials are rated for long term service at 180°F as well as for cold water applications. Hot and cold water distribution system piping made from these materials has a working pressure rating of 100 psi at 180°F. These systems are tested at 150 psi at 210°F for at least 48 hours to assure integrity at those condition, which may develop in the event the water heater controls malfunction. Thus, such materials are suitable for hot water distribution where water heaters are installed with relief valves set at 150 psi, 210°F.

All plumbing codes require the use of piping having the 100 psi @ 180°F rating for both the hot and the cold water portions of the water distribution system.

PEX tubing is manufactured by extrusion in sizes from ¼-inch -2 inch diameter to copper tube size, outside diameter controlled (CTS-OD) dimensions. The wall thickness is based on Standard Dimension Ratio 9 (SDR 9) values. It is available in coils and straight lengths.

PEX tubing may be installed below or above ground and in concrete slabs depending on local codes. Some codes may require sleeving the tubing, or where it penetrates a slab.

PEX tubing, because of its flexibility, is a good choice for manifold plumbing distribution systems. In these systems, individual tubing runs proceed from a manifold directly to each fixture in the house. Individual distribution lines are normally 3/8-inch or 1/2-inch, depending on fixture demand (GPM), length, service pressure, elevation, and required residual pressure. Since PEX tubing is flexible, most, if not all directional fittings behind the wall are eliminated. In manifold systems, one-piece PEX tubing is installed between the centrally located manifold and the fixture connection, thus the only joints are at the ends of the tube. Only a few additional joints are needed to complete the supply line to the header.

In North America, PEX tubing cannot be joined by solvent-cement nor heat fusion methods. A full line of mechanical directional and transition fittings are available. The joint is formed with various mechanical compression methods. The most widely available connection is the insert and crimp ring system produced to the ASTM F 1807 specification. This joining system is supplied by several manufacturers. As a general rule, fitting systems and installation tools used should be those recommended by the manufacturer of the tubing. Often, the suitable fitting information is roll marked on the tubing.

For further information on installing PEX, please consult the Installation Handbook provided by the Plastic Pipe and Fittings Association.

Manufacturers and Suppliers Participating in OPUS

Embassy Group LTD

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Ferguson

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MORSCO

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NIBCO INC.

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Uponor, Inc.

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Viega

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Watts Water Technologies

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Weldbend Corporation

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Winsupply

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Woodford Manufacturing Company

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Zurn Industries, LLC

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Applicable Joining Methods

PEX

There are several types of fittings for joining PEX. The various types of fittings are governed...
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