The demand for raw materials has increased over the years, mostly due to China’s rapid growth and expansion into the market.
The price of copper has risen considerably, which has led contractors, plumbers, and do-it-yourselfers to look for alternatives to copper pipe for water systems like cross-linked polyethylene (PEX).
Which is better copper or PEX pipe? PEX is better than copper piping for several reasons. PEX is a type of polymer tubing that costs much less than copper and is quicker to install. PEX tubing is also more flexible, requires fewer joints, and does not corrode like copper pipe. Having said that, copper still has advantages in some areas, like long-term durability, when properly installed and insulated.
There are many reasons that contractors and plumbers are switching to PEX tubing over copper pipe.
In this article, we’ll discuss the many benefits of cross-linked polyethylene (PEX) over copper piping in your water system so you can decide if you want to switch to PEX yourself.
Cross-Linked Polyethylene (PEX)
Cross-linked polyethylene (PEX or XLPE) is composed of polyethylene molecules that are “cross-linked” or bonded together in such a way that dramatically increases PEX’s wear resistance (source).
The cross-linking of the carbon atoms in PEX dramatically increases its strength and durability compared to other plastics like PVC.
Since the introduction of PEX in Europe during the 1970s, it has caught on rapidly. This increasing popularity is mainly due to the superior qualities of PEX in the realm of corrosion and temperature resistance (source).
Electricians and plumbers have used PEX in radiant heating and cooling, high-voltage electrical cables, and the water systems of domestic homes and buildings since the 1990s.
PEX Classification: PEX-a, PEX-b, & PEX-c
The most common methods of cross-linking molecules for PEX water pipe involve either peroxide (PEX-a) or silane (PEX-b), while there is also a method that uses UV radiation (PEX-c).
PVC (polyvinyl chloride), used mainly for drainage pipe, is a high-density form of polyethylene that is not cross-linked.
Manufacturing Standards: ASTM F876 and F877
The American Society for Testing and Materials (ASTM) has two primary standards for PEX pipe: ASTM F876 for regular PEX tubing, and ASTM F877 for distribution systems using hot and cold water (source).
All PEX manufacturers in the United States and Canada have to comply with both of these standards.
ASTM F876 covers PEX tubing cross-linked using peroxides (PEX-a), silane (PEX-b), Azo compounds, electron beam (PEX-c), or through any means that allow it to meet the required specifications. ASTM F876 rates tubing at three temperatures up to 200°F (source).
Overall, guidelines for F876 are more general than those of F877, covering basics like outside diameter, dimension ratios, pressure rate, burst rate, and the degree of cross-linking.
F876 has a maximum rated temperature of 200°F (93.3°C) with a maximum pressure rating of 80 PSI at that temperature. The maximum burst pressure of F876 is 480 PSI at 73.4°F (23°C) with a ½-inch tube.
The purpose of the ASTM F877 standard for pipe specifically intended for the hot and cold water system of both commercial and residential buildings. However, you can also use them for central heating systems.
ASTM F877 standard PEX is for water service of 100 PSI and with a maximum working temperature of 180 °F (82 °C). F877 standard tubing should be able to withstand a temperature of 210°F (98.9°C) at 150 PSI for a short period (around 48 hours).
ASTM F877 also specifies the types of fittings you can use, which go by ASTM standards F1960, F1961, F1807, and F1865. These include expansion fittings, compression fittings, and insert fittings using some copper crimp rings.
F877 also specifies the minimum hot and cold bending radius of the tubing. For hot, the minimum radius is 2.5 times the tube’s outside diameter, while, for cold, the minimum is 6 times the tube’s outside diameter.
Should I Replace Copper with PEX?
Any decision you make to replace copper tubing with PEX should take into consideration the age of your copper tubing, the extent of corrosion and leaks, chemical exposure, and the degree to which you experience freezing temperatures.
If you do decide to install PEX tubing yourself, make sure that you check your local building codes to make sure you’re compliant. There are still some jurisdictions that don’t allow you to use PEX. For well water, have your water tested for acidity or chlorine.
Advantages of PEX: Price
A PEX pipe system has several advantages over a copper pipe system, the most obvious of which is the price. The flexibility of PEX tubing also requires fewer fittings than copper pipe, which is good because PEX fittings tend to cost a little more (source).
Of the three classifications, PEX-a tends to be more expensive than either PEX-b or PEX-c, which are largely interchangeable.
Advantages of PEX: Accessibility
You can now find PEX tubing online or at your typical home improvement center in coils, making it very easy to ship or transport.
Some manufacturers only sell to plumbers, but nothing is preventing the do-it-yourselfer from replacing their copper pipe with PEX.
Typical PEX tubing comes in blue for cold water and red for hot water, although it also comes in white, grey, and black. Standard outside dimensions include ⅜-inch, ½-inch, ¾-inch, and 1-inch tubing, with larger sizes available.
Advantages of PEX: Ease of Installation
Another advantage of PEX is that installing PEX pipe requires much less skill than copper pipe since copper pipe requires you to use a torch to solder and sweat the pipe (source).
You can install PEX pipe using compression fittings with a wrench, and you can fit individual PEX lines to copper lines. In some applications, you can use PEX crimp pipe fittings and specially designed tools like the PEX-One 12V crimping tool.
Expansion-style fittings typically only work with peroxide cross-linked polyethylene (PEX-a). While you can use them with PEX-b and PEX-c, expansion fittings do not provide the same level of strength as when you use them with PEX-a (source).
The increased rigidity of PEX-b means that small cracks can form in the walls of the pipe when it expands. These cracks then weaken the connection of the fitting. PEX-b works best with crimp pipe fittings or clamp rings.
The Manifold System vs. Trunk-and-Branch
Many plumbers suggest installing PEX with a manifold system as the best option rather than a standard trunk-and-branch distribution system. In the trunk-and-branch line system, the water lines branch out from a larger supply line to specific fixtures (source).
With a manifold system, the supply lines go into a sort of circuit breaker-like manifold with multiple smaller lines going to the fixtures. One of the main advantages of this system is that you can shut off supply lines individually.
You would then use separate manifolds for hot and cold water lines. The addition of manifolds will tend to raise the price of your project, and all the lines can get a bit messy.
When choosing the size of your PEX pipe, you’ll need to remember that the inside diameter of the tube is less than that of copper pipe. Some plumbers recommend using ⅜-inch branch lines, but others recommend ½-inch branch lines from a 1-inch manifold (source).
What Lasts Longer: Copper or PEX?
Advantages of Copper: Longevity
Well-known home improvement specialists like to Bob Vila point out that copper does tend to last longer than PEX pipe at “50 to 70 years” compared to “30 to 50 years” for PEX (source).
Hot water over 180°F and high levels of chlorine in your water can significantly reduce the lifespan of PEX tubing, while acidic water is detrimental to copper.
PEX tubing comes in lifetime rating classes such as PE80 and PE100. At room temperature, PE80 can withstand hoop stress of 8 megapascals, while PE100 can withstand 10 megapascals over 50 years.
Under high stress, PEX tends to deform. PEX can also fail at low stress and can break apart if it has defects that lead to slow crack growth. One response to the need to increase fracture resistance has been the development of bimodal PE (source).
Bimodal polymers are materials that use two combined polymers with different molecular weights. The even distribution of these molecules allows for a pipe with increased durability without sacrificing fracture resistance (source).
Advantages of PEX: Freezing Temperatures
On the other hand, PEX, especially PEX-a, is capable of expanding and contracting better than copper, which is known to become damaged during cold winters.
Although, this is more of a problem for copper pipe in older homes since most modern homes are adequately insulated.
If you live in an area with frigid winters, it might be worth your time to swap out your copper pipe with a PEX system. Just bear in mind that PEX isn’t freeze-proof, it just resists breakage due to freezing temperatures better than copper pipe.
Advantages of PEX: Flexibility and Corrosion Resistance
PEX also resists chemical corrosion and does not suffer from the electrochemical corrosion of copper since it’s nonconductive. PEX also has better long-term resistance to pressure and reduces the number of joints required due to its flexibility.
This reduction of joints compared with rigid copper tubing has several benefits since this also reduces the chance of pinhole leaks, which are common with copper pipe joints (source).
Over time, pinhole leaks occur as chemical corrosion breaks down the copper at these weak points.
If you have hard water in your area, the corrosion of your copper pipe could be one cause of brown water in your water softener. Such hard water would be yet another good reason to switch to PEX pipe.
PEX-a is the most flexible of the three PEX classifications because it has the highest level of cross-linking.
Due to its elastic memory, you can use a heat gun to repair kinks in PEX-a. PEX-b, manufactured with the silane method, tends to be more rigid than peroxide-lined PEX-a and can be permanently damaged by such kinks.
Why is PEX Better than Copper Environmentally?
PEX is a petroleum product and not especially great for the environment on its own. Some plastic recyclers will not even accept PEX tubing.
This lack of scrap value can also be a plus since it reduces the risk of theft on a job site compared to using more valuable copper.
However, the methods used to extract and refine copper are even more harmful to the environment and energy-intensive compared to those used for PEX.
Advantages of PEX: It’s Energy Efficient
The main ways that PEX can be beneficial to the environment are by increasing energy efficiency as well as reducing water usage (source).
A National Association of Home Builders (NAHB) study found that a PEX manifold system and central demand heater could save you up to 35 percent on energy compared to a hot water tank with a copper tree-and-branch system (source).
The NAHB study also discovered significant energy savings regardless of the heater type used. Another environmental benefit is that PEX doesn’t corrode like copper and is not subject to the same kind of mineral buildup.
Disadvantages of PEX: It’s Gas Permeable
Unfortunately, PEX tubing is more susceptible to the environment than copper in some ways. This susceptibility is because regular PEX is permeable to gas, which is an obvious concern for water quality.
Carbon dioxide, chlorine, VOCs, and various other chemicals can enter your water through standard PEX tubing, so the quality of your local soil is another critical consideration.
In an article published in Water Science & Technology in 2007, M.L. Durand and A.M. Dietrich noted the degree to which PEX pipe that was cross-linked using silane (PEX-b) was permeable to chlorine and other solvents (source).
Similarly, in 2014, a nasty chemical spill in West Virginia contaminated the water supply of hundreds of thousands of residents, prompting the National Science Foundation to issue an award for studies on the permeability of PEX and PVC (source).
Non-Permeable Heating PEX
Durand and Dietrich suggested that the permeability of PEX might be offset by adding layers of nonpermeable material in between two PEX layers.
Currently, manufacturers have only accomplished this for heating applications with oxygen barrier PEX and PEX-AL-PEX.
Oxygen Barrier PEX
Several brands sell oxygen barrier PEX tubing, but they manufacture these for use in heating systems, while PEX used for plumbing is non-barrier. The design of oxygen-barrier PEX prevents the corrosion of iron fittings.
PEX-AL-PEX contains aluminum in between the layers of PEX, giving it a memory function as well as a barrier to oxygen. PEX-AL-PEX also uses its own unique fittings.
Some of the leading PEX tubing brands include Uponor, Bluefin, Mr. PEX, and ViegaPex. Make sure that you stick with one brand of PEX for tubing and fittings because mixing them will sometimes affect your warranty.
The leading brand is currently Uponor with its AquaPEX line and ProPEX expansion fitting system.
The fitting system includes several multiport tees and elbows. Uponor offers a 25-year warranty on all its pipe when you use their fittings; otherwise, the warranty is only 10 years (source).
The Department of Housing and Urban Development (HUD) issued a material release for Uponor AquaPEX in 2019, which they will review in 2022, accepting it as “suitable” for use in urban housing (source).
Uponor tubing is PEX-a class, which is the most flexible and the most expensive.
Mr. PEX tubing for plumbing uses peroxide cross-linked polyethylene, or PEX-a, with lead-free brass or PPSU fittings. They offer a 30-year warranty on their tubing and 2 years on the fittings (source).
When installed as a system, Mr. PEX offers a 10-year warranty on the entire system.
Viega produces PureFlow PEX tubing and their MiniBloc and ManaBloc manifolds.
This less-expensive PEX-b tubing comes with a 25-year warranty while the manifolds come with a 10-year warranty. The 25-year warranty, again, requires the use of the manufacturer’s fittings (source).
Bluefin PEX tubing for plumbing is also the cheaper PEX-b tubing. It comes in red, blue, and white, and the company offers a 25-year warranty (source).
Cross-linked polyethylene (PEX) tubing has several critical advantages over copper pipe. It’s much less expensive, and its flexibility makes it much easier to install.
The water runs quieter through it than copper pipe, and PEX tubing has more excellent resistance to mineral corrosion and freezing temperatures.
Under the rights circumstances, copper pipe still lasts longer than PEX tubing. If you have damaged sections of copper piping, it will be much cheaper to replace those sections with PEX tubing.
If you’re looking to conserve energy and save a little on your electric bill, PEX can save you up to 35 percent on energy. Just bear in mind that PEX pipe is more permeable to certain chemicals, unlike copper pipe.
Before you decide to install PEX pipe, check your local building codes. Whether you install it yourself or have someone else do it for you, you are not likely to regret it.