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With the new normal focusing on virus transmission and global human health, building owners and plumbing and mechanical contracting firms now must ensure the systems in their structures not only perform reliably, but also support indoor environmental quality. This includes system safety, hygiene, air quality, drinking water quality, comfort and energy efficiencies.
How does this pertain to a plumber? Well, a domestic water system in a structure has the responsibility of bringing water from the main source and distributing it throughout the building. When that water is running throughout all the piping, it has the potential to pick up various contaminants, depending on the type of system it is running through. For example, copper, brass and steel systems can corrode and experience scale buildup over time. That corrosion and scale buildup can impact the drinking water in a system — affecting everything from taste and odor to even bacterial formation.
Other piping systems, such as CPVC, use glues, cements and other chemicals to join the pipe to the fittings. These chemicals are not organic in nature and have the potential to pose risk if they seep into the drinking water system.
The safest material for drinking water requires a durable system that does not experience corrosion or scale buildup and also does not use chemicals for joining purposes. Enter PEX, or crosslinked polyethylene.
This polymer piping product has been used successfully in homes and commercial structures for decades. It naturally resists corrosion and scale buildup and offers several different joining methods, none of which use chemicals — or even an open flame, for that matter.
Best of all, PEX is a flexible piping product, so it greatly reduces the number of connections needed in a plumbing system. Instead of adding a fitting with each change in direction, the pipe simply bends in the direction needed for the design.
Joining PEX does not require the use of chemicals or open flame. There are actually a number of methods to connect the system when it is necessary to make a fitting.
The most popular among professional plumbers is the expansion system. This method uses a PEX-reinforcing ring on the end of the pipe and then requires an expansion tool to expand the pipe and ring so it can accommodate a fitting. As the pipe and ring shrink back to their normal size, a solid, strong connection is created onto the fitting that holds tight with thousands of pounds of radial force. Keep in mind that this connection method is designed specifically for PEX-a pipe, which offers the greatest amount of crosslinking during its manufacture. The result is a pipe that is more flexible with the most shape and thermal memory.
If you are unfamiliar with the different PEX types, here is a quick rundown:
PEX-a is manufactured using the Engel method. This produces a PEX with around 85% crosslinking of the polymer chains in the pipe. This is important because the greater the crosslinking, the more flexible and durable the pipe. It also provides shape and thermal memory that allows repairs of kinks in the pipe with a simple shot of heat from a heat gun.
PEX-b uses the Silane method, which produces 65% to 70% crosslinking, and PEX-c uses an electron beam to produce 70% to 75% crosslinking. These PEX manufacturing methods result in a stiffer piping product that is not as flexible as PEX-a and is also not viable for kink repairs. (This means you have to add a coupling if you get a kink in PEX-b or PEX-c pipe.) In addition, because of their lower crosslinking, these pipe types can experience micro-cracking when expanded. This can lead to leaks in fittings when using the expansion method.
There are several other joining methods for PEX pipe, including crimp and clamp, which use a smaller-diameter fitting that is inserted into the pipe and then a crimp ring or clamp ring fastens down around the outside of the pipe.
There are also push-to-connect, tool-less options, as well as expansion with compression, which uses expansion to insert a larger-diameter fitting. Then a compression sleeve is pulled over the outside of the pipe to hold the fitting in place.
While the push-to-connect option is quite easy and simple to make, some professionals prefer not to use it due to its questionable durability. Also, for the expansion-with-compression system, the two-step process of first expanding the pipe then adding the compression sleeve adds additional time to installs, which is not the most efficient.
When it comes to joining PEX piping systems, it’s important to know the pros and cons of each. For a complete rundown of each method, check out my past article on Making a Connection: A Comprehensive Guide to Putting Together PEX Pipe.
There are many resources for learning more about PEX piping systems and the benefits they offer. For example, you can visit the Plastics Pipe Institute website at plasticpipe.org or the Plastic Pipe and Fittings Association website at ppfahome.org to research all the different PEX manufacturers in North America.
You can also reference several of my past articles to learn about important points to know when designing and installing PEX. Here’s a list of a few:
Most PEX manufacturers offer a warranty on their piping systems, which is great. However, that warranty typically requires the system’s components be all one brand. That means, if you start mixing brands for the pipe, fittings, sleeves and rings, that warranty could become void.
Be sure you read and understand the warranty before you start your PEX installation. Your reputation and livelihood could depend on it.
Kim Bliss is the content development manager at Uponor. She can be reached at email@example.com.