PEX Plumbing Pipe

PEX Pipe: The New Alternative for Plumbing Installations

Radiant heating system manifold using PEX tubing
Chixoy/Wikimedia Commons/GFDL, License migration redundant, Self-published work CC BY-SA 3.0

PEX, or cross-linked polyethylene, is a plastic material used as a water supply piping systems that offers several advantages over copper, iron, lead and PVC plumbing pipes. PEX pipes provide superior heat resistance, long-term durability, and they are an excellent plumbing solution for fire-sprinkler systems. 

PEX is now one of the most innovative materials being used for water distribution systems, and its use grows every year.

PEX will become the dominant plumbing pipe in the near future.

PEX plumbing pipes should meet ASTM F876, ASTM F877, AWWA C904 and/or CSA B137.5 and they range in size from ¼-inch to 4 inches. Half an inch, ¾-inch and 1-inch are the most commonly used pipe sizes

PEX Plumbing Pipe Advantages

PEX plumbing pipe offers several advantages over older plumbing pipe materials: 

  • Much more resistant to freeze-breakage than copper or rigid plastic pipe.
  • Conserves energy by reducing heat transfer.
  • Eliminates the ‘water hammer’ noise usually found in copper pipe systems.
  • Shipped in spools, reducing shipping costs.
  • Flexibility offers additional storage options.
  • Available in various lengths and dimensions.
  • Doesn’t corrode over time.
  • Resists scale build-up common to copper piping.
  • Fittings do not require soldering.
  • Requires fewer connections and fittings, decreasing the chances for leaks. The flexible piping can be installed in 90-degree corners elbow fittings.
  • Can be installed faster than any other plumbing pipe.
  • Resists scale and chlorine.
  • Is less expensive than copper pipe.
  • Is accepted as a water distribution pipe in all major plumbing codes.

New Applications

PEX plumbing pipe has been used for several decades in European countries and has been introduced to the United States over a decade.

PEX pipes can be used for:

  • Plumbing and radiant floor heating applications.
  • Water service lines or potable distribution systems.
  • Heat transfer applications such as floor cooling, snow melting and permafrost protection.
  • Water distribution for hot water applications, including radiators.
  • Residential fire-sprinkler systems.

Limitations of Cross-Linked Polyethylene Plumbing

PEX plumbing pipe, though it offers many advantages, must also be treated carefully. 

  • PEX must be kept from contact with direct flame.
  • PEX should be protected from direct or indirect UV light.
  • PEX can be damaged if exposed to high concentrations of chlorine.
  • Avoid using PEX if it’s going to be installed in contaminated soils.
  • Pipe thread compounds, mineral or oil-based products should not be used with the pipe as these materials could alter the pipe’s characteristics or damage pipe fittings.
  • Installing the pipe near hazardous waste disposal sites or petroleum storage tanks is not recommended.
  • PEX fittings, particularly compression ones, are more expensive than copper fittings.

How to Identify PEX Tubing

PEX tubing is manufactured and classified by its outside diameter dimension, commonly called copper tube size (CTS). PEX pipes should be labeled, at least every five feet, with the following:

  1. The pipe’s manufacturer name or trademark.
  2. The pipe standard to which it conforms (ASTM F876, F877, AWWA C904 and/or CSA B137.5).
  3. Tube size and copper tube size.
  4. Plumbing pipe designation code (PEX0006 or similar).
  5. Pipe specified pressure/temperature rating(s).
  6. SDR9 ("Standard Dimension Ratio" or SDR is a ratio of the pipe's diameter to the wall thickness of the pipe; it is used by manufacturers to rate pressure piping).
  7. If the pipe is intended for potable water, it must be marked for suitability.
  8. ASTM fittings designations approved for use by the pipe manufacturer.