Choosing Pipe Fittings for PEX
When deciding which fittings to use for PEX piping there are a wide variety of products and tools available, as well as a variety of variables to consider, including costs, safety and ease of installation. If you don't do the research you could end up with major headaches, like getting sued due to groundwater contamination or a leaky system.
"There are so many choices for PEX fittings," said Marisa Chandley, senior marketing manager for Vanguard Plumbing, a company that sells PEX pipe and fittings. "What I would focus on is insuring that the fittings you purchase have an ASTM standard and are marked and certified by a third party agency like UL or NSF, or some other third party testing and listing agency."
Cheap brass fittings are being imported from China and Korea without a third party listing, Chandley said. They look an awful lot like fittings that do meet high standards. "Without that little mark on the side that says UL or NSF, you wouldn't know the difference."
If it is third-party certified, it is tested for health standards to make sure it's not leaching any unhealthy material into the groundwater. "Obviously there is a contamination concern if it is not listed or tested," Chandley said. Because of problems with polybutylene, PEX's predecessor, all plastic fittings are listed. "Primarily, because there is a fear in the marketplace over plastic not performing, [plumbers] really want to cover themselves when they buy a plastic fitting," Chandley said.
For standard applications, Chandley recommends brass fittings. "But in areas where water is very acidic or you have contamination concerns, plastic fittings are definitely preferable," she added. In hot soils or acidic water conditions, brass tends to corrode and can cause a failure over time. "There are times when you would definitely want to use a brass fitting. For example, when you might be exposed to certain chemical agents at the application. Plastic does not react well -- depending upon the kind of plastic -- to certain chemical contaminants (including solvents and pesticides that have a petroleum base). If there is ever a concern, generally speaking, you're safer to go with a brass or a copper fitting."
For some contractors, the ease of installation is the key factor in deciding which fittings to purchase. However, there is a tradeoff. You may have to spend more money for installation tools on the faster systems.
According to Chandley, the easiest and most popular scenario is a brass insert fitting with a copper crimp ring. "They fit in and you simply use a tool that clamps that crimp ring down tight around the fitting and you're done in a few seconds." However, you have to have a different tool for each size of pipe. Estimated cost is $120 per tool.
Another fitting resembling a hose clamp goes around the outside of the PEX pipe and crimps down over an insert fitting. "That only takes one tool, but it takes a little more time and if it's over-crimped the clamp will break, so there's a little more waste in that type of installation."
According to David Holdorf, engineering manager for RTI Pex Piping Systems, a brass fitting tends to allow for a better surface for the PEX to grab on to. "You can get a better quality control out of it because you can get a nice strong barb coming off of the fitting to really make a bite into the PEX tubing, whereas with a thin copper fitting you might see those barbs a little more rounded and not as sharp as a brass fitting." Brass also lasts longer than copper in aggressive situations, he said.
Holdorf’s company produces the Plumb-PEX system. They utilize a stainless steel band that tightens around the PEX. "It does the same thing as the copper (crimp) ring. We just have more control over how much pressure is put on the system with the stainless steel band." They provide all three different major kinds of fittings, with 90 percent of the fittings sold made of brass, while 8 percent are plastic and 2 percent are copper.
The Plumb-PEX ratchet tool, which is what RTI uses to connect the stainless steel clamp, is a one-sized tool that fits all sized pipes, which will work between 3/8th and 1-inch PEX tubing. "There is no calibration needed,” Holdorf pointed out. “When you make a connection, you have a 100 percent connection every single time when the tool is released from the clamp." Cost is about $100.
Holdorf suggests that contractors take the time to investigate each product -- both the PEX pipe and the fittings -- before spending money. "Most PEX manufacturers have their own connection systems. One of the pitfalls can be discovering you like another company's fittings better than the one that manufactured the pipe. See what they have to offer with regard to the installation method and the speed and the quality of the connection." He also cautions that most of the major PEX manufacturers warranties are void if you do not use their fittings.
"There are a lot of manufacturers out there, so it's very important to make sure to get it from a reputable source who has quality control," said Andy Fiefhaus, vice president and general manager of Stadler-Viega, a 102-year-old company and European market leader. "Everybody is making PEX up to a standard, but you have to consider that the standard is a minimum requirement for a product."
Stadler-Viega has forsaken brass and copper, now producing only bronze fitting systems. Fiefhaus said bronze prevents de-zincification and is therefore more corrosion resistant.
"If you have regular brass you have a lot of zinc in the fitting system and depending on the water quality you can have a reaction called de-zincification [which] allows for corrosion. Our fittings consist of a bronze fitting, bronze inset fitting and a stainless steel sleeve. The stainless steel sleeve is pushed over the tubing and then you insert the fitting. Then you take a tool and you hold it over the press leaf and then you push it and it only releases when you apply the right amount of pressure. The tool presses the sleeve to the tubing, which again presses the tubing against the fitting and it guarantees a fast, very safe connection." Tool list price is $229. A different tool is needed for each pipe dimension.. Stadler-Viega offers 2/2-, 3/4- and one-inch pipe. They also offer a 3/8s size that is used rarely.
Fiefhaus said his company does not feel comfortable providing plastic fittings. "There's not enough history in 'R & D' from our viewpoint, in this type of material at this point. I'm not saying it can't be done. There are fitting systems out there and they are working. We need a little more convincing that this is the way to go for us."
Randy Knapp is brand manager/plumbing of Wirsbo, which has been making PEX pipe since 1970. "If you are going to have a feeling of comfort, a fitting system should be proven over time, meaning it has gone through a lot of development, a lot of testing," Knapp said. "You need to go with a proven track record, because what it really boils down to is few systems have proven themselves." Knapp also pointed out that Wirsbo's "Pro-PEX" cold expansion fittings -- available in brass or engineered plastic -- are certified.
"It's a fitting that's very simple to do,” Knapp said. “You expand the pipe a set number of times, and then you're utilizing the properties of the PEX material to affect the seal on the fitting. PEX tubing wants to go to its original shape. With a Pro-PEX fitting, the properties of material are working for you, instead of against you. On a half-inch you expand the pipe three times, you put the fitting in and basically you can do a pressure test immediately. You are done in very short order. You don't have any cure times and you don't have any heat issues."
Wirsbo’s system utilizes a manual expander tool that performs expansions and compression for pipe 3/8s through one inch. Two tools are needed for pipe over one inch. Wirsbo does sell a single battery-operated unit that does all of the work for all sizes of pipe. Manual tools cost about $500, while the battery unit sells for $1,850.
Knapp stresses the importance of making sure a vendor company provides outstanding technical support and training. "We train every plumber we come into contact with -- so it's ten of thousands of plumbers in face-to-face trainings. It could be a group of two or 20. We'll go out and make sure they understand the practices of PEX and that they know exactly how to make a fitting and a connection. There are certain places (jurisdictions) where approvals require that training take place for each of the installers.”
Lance MacNevin, unit manager for REHAU’s Heating and Plumbing group, offered his advice on fitting selection: "When evaluating a fitting system, a contractor must imagine assembling it in cold, wet weather, in a confined space with dark lighting," MacNevin said. "Even though many fitting designs will work fine in the laboratory, the real-world is tougher, with stresses on joints, potential for assembly errors and longer lifetimes than what is used in accelerated laboratory testing," he said. "The long-term conditions of the application must also be considered: A normal plumbing system is not as demanding as a continuous re-circulation or hot water heating application, where pipe and fittings are hot most or all of the time. A fitting with a proven history of performance is important."
While PEX pipe has proven to be corrosion resistant, it is also important to make sure that your fittings are too, MacNevin said. "Water across the country varies in pH, hardness and mineral content. Treated drinking water may also have additives that can affect pipes and fittings. Brass fittings have proven to be corrosion resistant in drinking water, but reverse osmosis treatment (and its propensity for damaging metal fittings) introduces new challenges for the fitting material."
PEX pipes intended for plumbing applications are now required to prove their chlorine resistance, according to test method ASTM F 2023. Any fitting used with PEX pipe in a plumbing system must be at least as chlorine-resistant as the pipe.
MacNevin stressed the importance of making sure that both the pipe and the fitting are certified to ASTM standards and that they must be compatible. "Not all PEX fittings are compatible with all PEX pipes. This may be because different pipes have differing properties, in terms of flexibility and strength. The pipe should be marked with the same ASTM standard number as the fitting."
Wirsbo and REHAU are the only manufacturers who produce cold expansion fittings. While Wirsbo uses PEX rings, REHAU utilizes metal compression sleeves.
MacNevin says the two cold expansion systems outdistance other fittings because they allow for better flow. "They're bigger fittings because we expand the pipe. It allows for better water flow and less pressure reduction."
Both the Wirsbo and REHAU methods provide the same diameter within the fitting . The difference is in the application system. MacNevin said the REHAU method does not rely on the "memory" of the pipe. "As soon as we expand our pipe, we put our fitting in and we use our compression tool to pull the sleeve up over the pipe to compress the pipe over the insert and it's done right away. Regardless of the weather or the temperature our fitting is always completed in about 20 seconds. Overall, it's a faster fitting system."
A combination expansion and compression tool, known as COMBOLOC, is used to install 3/8- and 1/2-inch pipe. All other sizes need two tools. Cost for a kit, which has tools for all pipes, is $500. Cost for the combo tool is $125 to $150. The tools needed for only the larger sizes are $350.
There are three other less popular fittings on the market:
*Push type fittings. Limited in use; they are mostly seen in the RV industry. They are available at do-it- yourself shops and do not have an ASTM standard.
*A multi-piece brass fitting called a Schluep. It involves use of a special torque sensing wrench to join the two pieces together. You end up with a threaded end and you have to buy special threaded T's and elbows and join it again. In other words, you have to build your fittings as you go.
*Standard compression fittings. According to Holdorf, they are not used much in the plumbing side, but in the heating end of the business. "It’s a split ring compression. There are no tools needed. It's just got a ferrule that goes over the outside of the tubing and it's tightened down with a nut." Drawback is the three piece fittings cost three to four times more than most systems.