Crimp, expansion, compression, press sleeve, Everloc ™, Wirsbo ™ ….what are they all and what do they mean? There are many different types of PEX fittings and we are asked all the time what they are and more importantly how they work. The major types of PEX fittings include metal or plastic insert fittings using either a crimp ring or a stainless steel clamp, cold-expansion fittings and push fittings.
- F1807 and F2159 Crimp Fittings
These insert fittings use a crimp ring that is compressed around the PEX tubing and they can be made from either metal or plastic insert fittings. The compression of the crimp ring crushes the pipe around the insert barb and ensures that the fitting is secured. When these fittings are made of brass they are regulated by standard ASTM F1807, and can be used with PEX-a, PEX-b, or PEX-c. Generally in the industry, they are considered to be primarily PEX-b or PE-RT fittings and are often referred to simply as “Brass Pex Fittings” or “Crimp Fittings”. When these fittings are made of plastic or polymer they are regulated by standard ASTM F2159, Generally in the industry, they are considered to be primarily PEX-b or PE-RT fittings and are often referred to simply as “Plastic Pex Fittings” or “Crimp Fittings”. For both types of fittings, before the connection is made, the crimp ring slides over the end of the PEX tubing, away from the end of the tube. The fitting is inserted into the end of the tube and the crimp ring is aligned and compressed. Since the fitting is a smaller diameter than the tubing, it restricts water flow. This can pose the need for an upsizing of the piping system. Furthermore, the strength of a crimp fitting is highest when the connection is first made, as over time the PEX tubing will resist the crimp ring fitting, especially PEX-a or PEX-c.
- F2098 Stainless Steel Clamp Fittings
Stainless steel clamp fittings work very similarly to the crimp fitting process; however, instead of using a copper crimp ring like in the process for both the F1807 and F2159 fittings, a stainless steel clamp ring is used for ASTM F2098 fittings.
- F1960 and F2080 Cold-Expansion Fittings
Cold-expansion fittings are full flow plumbing and hydronic fittings with the same inside diameter as the tubing. There are two types of cold expansion fittings, which use a pex expansion ring or a compression ring respectively. ASTM F1960 fittings use an expansion pex ring which slides over the PEX and a tool is used to expand the ring and tubing at the same time, before the fitting barb is inserted. These fittings can be made of polymer or brass and are secured as both the ring and the tubing contract over time against the fitting. It is important to note that this connection type should only be installed when the temperature is above 5 °F (-15 °C), as the pipe and pex ring. Also, cold-expansion fittings are only suitable for use under a pressure of 100 psi and at a maximum temperature of 180 °F (82 °C). The ASTM F1960 cold-expansion fittings are likely to be referred to as “Propex” or “Wirsbo” and are used with PEX-a and PEX-c. This fitting is generally considered the most reliable and will strengthen over time as PEX contracts. In addition, this fitting is full flow, as they have the same inside diameter as the PEX tubing. Some brands of PEX-b and PE-RT have been certified for use with this fitting type; however, notably they still require the use of an expansion ring made of PEX-a or PEX-c, as neither B-pex or pe-rt pipe will naturally contract on their own. The second type of cold expansion fitting is regulated by standard ASTM F2080 and is commonly referred to as “Everloc” or “Rehau” fittings. These are also suitable only for use with materials that possess thermal or shape memory characteristics, which are PEX-a and PEX-c. In this fitting process, a metal compression sleeve is first placed over the tube. The tubing is then expanded until the fitting barb can be inserted, and then the compression sleeve is drawn down over the fitting until there is contact between the metal sleeve and the shoulder of the fitting. Unlike F1960 fittings, F2080 has no restriction on installation temperature, or operating temperatures and pressures, and they have the ability to be pressure tested immediately. This makes F2080 the most secure form of PEX connection. The primary drawback is that two different tools are required to complete an F2080 connection.
- F2854 Push Fittings
Push fittings, often commonly referred to as “Sharkbite” are connected by a means of pushing the tube into the fitting. The fitting is connected due to the forces produced by the mechanism inside of the fitting pressing against the outside wall of the pipe. Push fittings are regulated by standard ASTM F2854, and can be used with PEX-a, PEX-b, PEX-c, PE-RT, CPVC and Copper. This connection does not require any additional tools and the fittings can be removed and reused. This makes push fittings very versatile and a very quick and efficient way to install a plumbing system, and a great choice for DIY savvy homeowners. In some cases, a stiffening sleeve may be inserted into the PEX tubing for these fittings, to keep the PEX tubing rigid and to make a seal against the O-ring inside of the fitting. It should be cautioned that some jurisdictions do not allow push fittings to be used in all applications and there have been documented cases of fitting failures on hydronic heating systems where the constant high water temperature fluctuations have weakened the fitting. Now, after investigating the different types of PEX and PEX fittings, you will have a better understanding of how your system will work. For any further questions or guidance, our design and engineering team are available and can be contacted. Keep Calm and Plumb On!
AWWA C904 Subcommittee of the Standards Committee on Polyolefin Pressure Pipe and Fittings. “Committee Report: Design and Installation of Cross-Linked Polyethylene (PEX) Pipe in Accordance with AWWA C904.” Journal (American Water Works Association), vol. 104, no. 3, 2012, pp. 68–79. JSTOR,
www.jstor.org/stable/jamewatworass.104.3.68. Accessed 1 Mar. 2021.
ASTM F1807-19b, Standard Specification for Metal Insert Fittings Utilizing a Copper Crimp Ring, or Alternate Stainless Steel Clamps, for SDR9 Cross-linked Polyethylene (PEX) Tubing and SDR9 Polyethylene of Raised Temperature (PE-RT) Tubing, ASTM International, West Conshohocken, PA, 2019, www.astm.org
ASTM F2159-20, Standard Specification for Plastic Insert Fittings Utilizing a Copper Crimp Ring, or Alternate Stainless Steel Clamps for SDR9 Crosslinked Polyethylene (PEX) Tubing and SDR9 Polyethylene of Raised Temperature (PE-RT) Tubing, ASTM International, West Conshohocken, PA, 2020, www.astm.org
ASTM F2098-18, Standard Specification for Stainless Steel Clamps for Securing SDR9 Cross-linked Polyethylene (PEX) Tubing and SDR9 Polyethylene of Raised Temperature (PE-RT) to Metal Insert and Plastic Insert Fittings, ASTM International, West Conshohocken, PA, 2018, www.astm.org
ASTM F876-20b, Standard Specification for Crosslinked Polyethylene (PEX) Tubing, ASTM International, West Conshohocken, PA, 2020, www.astm.org
ASTM F1960-20, Standard Specification for Cold Expansion Fittings with PEX Reinforcing Rings for Use with Cross-linked Polyethylene (PEX) and Polyethylene of Raised Temperature (PE-RT) Tubing, ASTM International, West Conshohocken, PA, 2020, www.astm.org
ASTM F2080-19, Standard Specification for Cold-Expansion Fittings with Metal Compression-Sleeves for Crosslinked Polyethylene (PEX) Pipe and SDR9 Polyethylene of Raised Temperature (PE-RT) Pipe, ASTM International, West Conshohocken, PA, 2019, www.astm.org
ASTM F2854-20a, Standard Specification for Push-Fit Crosslinked Polyethylene (PEX) Mechanical Fittings for Crosslinked Polyethylene (PEX) Tubing, ASTM International, West Conshohocken, PA, 2020, www.astm.org