Hydronic Piping: PEX Tubing

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Hydronic is a term used to describe a heating or cooling system that transfers heat by...

Cross-Linked Polyethylene (PEX) is a thermoset material made from medium or high density,...

Benefit of Material to Systems Application

PEX is widely used for radiant floor heating and other hydronic heating systems. Introduced into the United States in the 1980s, PEX has replaced polybutylene (PB) as the most widely used flexible plumbing piping. Flexible systems are generally easy to install and service and are quieter than rigid piping. PEX is able to withstand the high and low temperatures found in heating applications, and is highly resistant to chemicals found in the plumbing environment. The smooth interior resists scale buildup and corrosion that can affect long term pipe flow characteristics. PEX is also very freeze-break resistant. 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. Cost saving benefits of PEX include lower installed cost, fewer fittings, less labor and decreased potential for leaks. PEX systems are well suited to multiple layouts, such as manifold, remote manifold and traditional trunk and branch. PEX pipe is approved for hot-water (hydronic) heating systems in all model plumbing and mechanical codes across the U.S. and Canada. PEX is not intended for outdoor or UV exposed applications.

System Application and Material Usage

PEX radiant tubing can be installed in a concrete mass called gypsum concrete or "Gypcrete." However, it is increasingly installed in a low-mass or modular board underlayment system where, rather than embedding the hot water tubing in concrete, the PEX tubing is laid in the grooves of pre-cut wood panels. This method is ideal for remodeling and most new construction projects. In many hydronic applications, it is recommended that PEX tube with an Oxygen Barrier be used to minimize the potential for corrosion of any ferrous components in the heating system.

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 1/4-inch to 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. Some codes may require sleeving the tubing where it penetrates a slab.

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.

Manufacturers and Suppliers Participating in OPUS

F.W. Webb Company

F.W. Webb Company is a multi-faceted distributor of plumbing and heating, HVAC and controls,......
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Ferguson specializes in providing PVF, Plumbing, HVAC and Related Specialty Products and......
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Hajoca Corporation

Founded in 1858, the Hajoca Corporation is the largest privately owned wholesale distributor of......
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Jomar Valve

Founded in 1966 by former Navy Commander Joseph Martin, Jomar Valve set out to change the way......
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MORSCO is a leading U.S. distributor of commercial and residential plumbing, HVAC, and PVF, with......
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The Commonwealth Group

The Commonwealth Group is the industry’s newest, 100-percent member owned, $8.5......
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Uponor, Inc.

Uponor (formerly Wirsbo) is the leading supplier of radiant heating and cooling and plumbing......
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Founded in 1899, Viega manufactures and distributes the highest quality plumbing, heating and......
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Watts Water Technologies

Watts Water Technologies  designs and manufactures valves and related fluid handling......
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Weldbend Corporation

Weldbend Corporation is a manufacturer of carbon steel welding fittings and forged steel......
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WinWholesale, Inc. is comprised of over 525 wholesale distribution locations. Along with Noland......
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Zurn Industries, LLC

Zurn Industries markets and manufactures roof/floor drains, interceptors, cleanouts, water......
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Applicable Joining Methods


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