PEX – easier, cheaper, and more pliable than copper.

But while generally assumed to be an adequate replacement for copper, during a home inspection it is imperative to know whether or not it is acceptable as a water supply piping material

This creates a potential defect during the home inspection prior to a purchase. First, the very use of PEX may not be approved as acceptable to code. Will PEX alone be considered a code violation? Most likely not, as defects and code violations are not exactly the same. Depending on the town and the code on their books, it seems unlikely that a builder would knowingly create an obstacle to purchasing a home or multi-family dwelling.

That said, let’s look at the basics of PEX, what you need to know as a purchaser, what questions you should ask a home inspector and why it remains somewhat controversial even as the use of it continues to grow across the United States.

What is PEX Water Supply Piping?

Air Conditioning System MaintenanceIntroduced into the US in the 1980’s, PEX Water Supply Piping is made from a cross-linked, high-density polyethylene (HDPE) polymer. The process of manufacturing PEX consists of melting the polymer as a means of manufacturing the tubes.

Strength, flexibility, and durability to the polymer are added by crosslinking. There are different manufacturers who may use the Engels method, the Silane method or the radiation method to create the necessary chemical reaction that triggers crosslinking. Crosslinking helps PEX resist cracking, impact damage and extremely cold temperatures.

The PEX tube manufactured to CTS-OD sizes is the most common, with available sizes including 3/8″, 1/2″, 5/8″, 3/4″ and 1″. On the website, “PEX tube” refers to this common CTS-OD product (copper tubing size, outside diameter, controlled) sizes, commonly with a standard thickness of SDR-9 (standard dimension ratio). PEX pipe may be manufactured to IPS-ID (iron pipe size, inside diameter, controlled) sizes with varying thickness to meet pressure requirements

What are the Primary Advantages of PEX?

PEX in New ConstructionAccording to the industry website, the biggest advantage of PEX is its flexibility. Instead of cutting lengths of copper, galvanized or PVC and creating bends and turns with fittings and connectors, PEX wraps around corners and other unusual shapes in one piece. Fewer fittings mean fewer spots where leaks might occur, and there is less need for glue or solder. also lists these pluses:

  • Less expensive than copper, and less likely to break or burst in freezing conditions
  • No corrosion
  • No lime or scale buildup
  • Lower heat transfer/heat loss to save energy
  • Quieter than copper and much less likely to produce water hammer
  • Less labor intensive than any traditional piping

What are the Disadvantages?

Although PEX is a seemingly ideal solution for anything from piping the whole interior of the home to running heated water through a radiant home heating system, it’s not perfect. Perhaps the most prominent disadvantage is its lack of resistance to UV damage. That’s one reason why, even in areas where it’s up to code, it’s still not used outside the home.

Buildipedia also says the color-coded tubes might not look as attractive as copper, which doesn’t matter in concealed spaces but might in an exposed basement installation. If the tubing is ever exposed to temperatures above 180 F at 100 psi, the tubing is prone to failure.

Is PEX an Automatic Home Defect?

PEX Crimp ToolMany areas of the United States have embraced PEX for its numerous benefits, but some locations are still skeptical. For that reason, the flexible tubing might be a code violation in your area. That said, a code violation doesn’t always equal a defect.

Home defects are issues that impair the usability of the home, put the homeowners at a health or safety risk, put the structure at risk or all three. Unless PEX is damaged or improperly installed, it’s not a defect in the strictest definition.

What is it about this flexible, convenient tubing that makes some locations throw up a caution flag or forbid it altogether? Inexperience with installation and a fear of the unknown are probably two major factors. But as more locations embrace PEX, expect to see it emerge as another common piping solution, not just a new gadget.

The Hidden Weakness

PEX clamp removalPEX has a hidden weakness which has become the subject of numerous home inspection failures. And it has nothing to do with the pipes or tubes themselves. It has everything to do with the choice of fittings and the skill of the installer/plumber to do what could be hundred of crimps, done by hand, sometimes in tight spaces. The repetitive nature of crimping without specific torque specifications that many fittings should require is essentially defined by the instruction and mentoring of plumbing apprentices. A standard of “Good and Tight” may result in the development of a “weeping loss” something less than a visible drip that allows water to escape. A full pressure test of an entire system is generally too expensive and considered unnecessary by new home builders. However, there are several fitting methods which can be used.

Standard Fitting Method

The standard method for connecting PEX pipe to brass PEX fittings uses a copper crimp ring and a PEX crimping tool. The copper crimp ring is inserted over the pipe, the fitting is inserted inside the pipe, and the copper ring is crimped over the pipe and fitting using the PEX crimping tool.

Expansion Fitting Method

The expansion method involves using an expansion tool to increase the diameter of the PEX tube. Special expansion fittings are inserted into the expanded tube, which shrinks back to shape around the fitting. A plastic ring is then pressed over the fitting to insure a tight connection.

SSC Method

The SSC (stainless steel clamp) method uses special clamps designed for PEX connection. The fittings used here are the same used in the “Standard Connection Method” above, but in this method, the SSC fastens the PEX tube to the fitting. A special “SSC crimping tool” is used to tighten the clamp around the tube.

Compression Method

Standard compression fittings can be used to make connections between PEX tubing. For moderate to large size jobs, this method is more expensive than using the Standard Connection Method since compression fittings cost more than PEX fittings.

“Push-fit” and other proprietary methods

Several companies offer specialized fittings that will connect PEX to PEX or to copper, PVC, and other materials as well. These fittings use one or more of several technologies such as EDPM O-ring seals, stainless steel gripping teeth, and threaded compression nuts. These fittings are faster and easier than most competing methods, but cost more per fitting than standard PEX fittings.

Summary: While there is truly no good reason to avoid considering a home using PEX for water supply, it becomes a strong reason to hire a qualified home inspector. The inspector will check for any loose fittings, damp or “weeping” fittings, and where PEX pipes are connected to copper or other types of water supply piping material – PVC, Galvanized Steel, and brass. If any issues are found after the inspection, they can be addressed before the closing. PEX is a wonderful product, but as long as humans are responsible for their connections and installation, it remains a fact that problems can occur. Minimize these problems with a home inspection.